research conclusion importance

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Organizing Your Social Sciences Research Paper

• 9. The Conclusion
• Purpose of Guide
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The conclusion is intended to help the reader understand why your research should matter to them after they have finished reading the paper. A conclusion is not merely a summary of the main topics covered or a re-statement of your research problem, but a synthesis of key points derived from the findings of your study and, if applicable, where you recommend new areas for future research. For most college-level research papers, two or three well-developed paragraphs is sufficient for a conclusion, although in some cases, more paragraphs may be required in describing the key findings and their significance.

Conclusions. The Writing Center. University of North Carolina; Conclusions. The Writing Lab and The OWL. Purdue University.

Importance of a Good Conclusion

A well-written conclusion provides you with important opportunities to demonstrate to the reader your understanding of the research problem. These include:

• Presenting the last word on the issues you raised in your paper . Just as the introduction gives a first impression to your reader, the conclusion offers a chance to leave a lasting impression. Do this, for example, by highlighting key findings in your analysis that advance new understanding about the research problem, that are unusual or unexpected, or that have important implications applied to practice.
• Summarizing your thoughts and conveying the larger significance of your study . The conclusion is an opportunity to succinctly re-emphasize  your answer to the "So What?" question by placing the study within the context of how your research advances past research about the topic.
• Identifying how a gap in the literature has been addressed . The conclusion can be where you describe how a previously identified gap in the literature [first identified in your literature review section] has been addressed by your research and why this contribution is significant.
• Demonstrating the importance of your ideas . Don't be shy. The conclusion offers an opportunity to elaborate on the impact and significance of your findings. This is particularly important if your study approached examining the research problem from an unusual or innovative perspective.
• Introducing possible new or expanded ways of thinking about the research problem . This does not refer to introducing new information [which should be avoided], but to offer new insight and creative approaches for framing or contextualizing the research problem based on the results of your study.

Bunton, David. “The Structure of PhD Conclusion Chapters.” Journal of English for Academic Purposes 4 (July 2005): 207–224; Conclusions. The Writing Center. University of North Carolina; Kretchmer, Paul. Twelve Steps to Writing an Effective Conclusion. San Francisco Edit, 2003-2008; Conclusions. The Writing Lab and The OWL. Purdue University; Assan, Joseph. "Writing the Conclusion Chapter: The Good, the Bad and the Missing." Liverpool: Development Studies Association (2009): 1-8.

Structure and Writing Style

I.  General Rules

The general function of your paper's conclusion is to restate the main argument . It reminds the reader of the strengths of your main argument(s) and reiterates the most important evidence supporting those argument(s). Do this by clearly summarizing the context, background, and necessity of pursuing the research problem you investigated in relation to an issue, controversy, or a gap found in the literature. However, make sure that your conclusion is not simply a repetitive summary of the findings. This reduces the impact of the argument(s) you have developed in your paper.

When writing the conclusion to your paper, follow these general rules:

• Present your conclusions in clear, concise language. Re-state the purpose of your study, then describe how your findings differ or support those of other studies and why [i.e., what were the unique, new, or crucial contributions your study made to the overall research about your topic?].
• Do not simply reiterate your findings or the discussion of your results. Provide a synthesis of arguments presented in the paper to show how these converge to address the research problem and the overall objectives of your study.
• Indicate opportunities for future research if you haven't already done so in the discussion section of your paper. Highlighting the need for further research provides the reader with evidence that you have an in-depth awareness of the research problem but that further investigations should take place beyond the scope of your investigation.

Consider the following points to help ensure your conclusion is presented well:

• If the argument or purpose of your paper is complex, you may need to summarize the argument for your reader.
• If, prior to your conclusion, you have not yet explained the significance of your findings or if you are proceeding inductively, use the end of your paper to describe your main points and explain their significance.
• Move from a detailed to a general level of consideration that returns the topic to the context provided by the introduction or within a new context that emerges from the data [this is opposite of the introduction, which begins with general discussion of the context and ends with a detailed description of the research problem]. 

The conclusion also provides a place for you to persuasively and succinctly restate the research problem, given that the reader has now been presented with all the information about the topic . Depending on the discipline you are writing in, the concluding paragraph may contain your reflections on the evidence presented. However, the nature of being introspective about the research you have conducted will depend on the topic and whether your professor wants you to express your observations in this way. If asked to think introspectively about the topics, do not delve into idle speculation. Being introspective means looking within yourself as an author to try and understand an issue more deeply, not to guess at possible outcomes or make up scenarios not supported by the evidence.

II.  Developing a Compelling Conclusion

Although an effective conclusion needs to be clear and succinct, it does not need to be written passively or lack a compelling narrative. Strategies to help you move beyond merely summarizing the key points of your research paper may include any of the following:

• If your essay deals with a critical, contemporary problem, warn readers of the possible consequences of not attending to the problem proactively.
• Recommend a specific course or courses of action that, if adopted, could address a specific problem in practice or in the development of new knowledge leading to positive change.
• Cite a relevant quotation or expert opinion already noted in your paper in order to lend authority and support to the conclusion(s) you have reached [a good source would be from your literature review].
• Explain the consequences of your research in a way that elicits action or demonstrates urgency in seeking change.
• Restate a key statistic, fact, or visual image to emphasize the most important finding of your paper.
• If your discipline encourages personal reflection, illustrate your concluding point by drawing from your own life experiences.
• Return to an anecdote, an example, or a quotation that you presented in your introduction, but add further insight derived from the findings of your study; use your interpretation of results from your study to recast it in new or important ways.
• Provide a "take-home" message in the form of a succinct, declarative statement that you want the reader to remember about your study.

III. Problems to Avoid

Failure to be concise Your conclusion section should be concise and to the point. Conclusions that are too lengthy often have unnecessary information in them. The conclusion is not the place for details about your methodology or results. Although you should give a summary of what was learned from your research, this summary should be relatively brief, since the emphasis in the conclusion is on the implications, evaluations, insights, and other forms of analysis that you make. Strategies for writing concisely can be found here .

Failure to comment on larger, more significant issues In the introduction, your task was to move from the general [the field of study] to the specific [the research problem]. However, in the conclusion, your task is to move from a specific discussion [your research problem] back to a general discussion framed around the implications and significance of your findings [i.e., how your research contributes new understanding or fills an important gap in the literature]. In short, the conclusion is where you should place your research within a larger context [visualize your paper as an hourglass--start with a broad introduction and review of the literature, move to the specific analysis and discussion, conclude with a broad summary of the study's implications and significance].

Failure to reveal problems and negative results Negative aspects of the research process should never be ignored. These are problems, deficiencies, or challenges encountered during your study. They should be summarized as a way of qualifying your overall conclusions. If you encountered negative or unintended results [i.e., findings that are validated outside the research context in which they were generated], you must report them in the results section and discuss their implications in the discussion section of your paper. In the conclusion, use negative results as an opportunity to explain their possible significance and/or how they may form the basis for future research.

Failure to provide a clear summary of what was learned In order to be able to discuss how your research fits within your field of study [and possibly the world at large], you need to summarize briefly and succinctly how it contributes to new knowledge or a new understanding about the research problem. This element of your conclusion may be only a few sentences long.

Failure to match the objectives of your research Often research objectives in the social and behavioral sciences change while the research is being carried out. This is not a problem unless you forget to go back and refine the original objectives in your introduction. As these changes emerge they must be documented so that they accurately reflect what you were trying to accomplish in your research [not what you thought you might accomplish when you began].

Resist the urge to apologize If you've immersed yourself in studying the research problem, you presumably should know a good deal about it [perhaps even more than your professor!]. Nevertheless, by the time you have finished writing, you may be having some doubts about what you have produced. Repress those doubts! Don't undermine your authority as a researcher by saying something like, "This is just one approach to examining this problem; there may be other, much better approaches that...." The overall tone of your conclusion should convey confidence to the reader about the study's validity and realiability.

Assan, Joseph. "Writing the Conclusion Chapter: The Good, the Bad and the Missing." Liverpool: Development Studies Association (2009): 1-8; Concluding Paragraphs. College Writing Center at Meramec. St. Louis Community College; Conclusions. The Writing Center. University of North Carolina; Conclusions. The Writing Lab and The OWL. Purdue University; Freedman, Leora  and Jerry Plotnick. Introductions and Conclusions. The Lab Report. University College Writing Centre. University of Toronto; Leibensperger, Summer. Draft Your Conclusion. Academic Center, the University of Houston-Victoria, 2003; Make Your Last Words Count. The Writer’s Handbook. Writing Center. University of Wisconsin Madison; Miquel, Fuster-Marquez and Carmen Gregori-Signes. “Chapter Six: ‘Last but Not Least:’ Writing the Conclusion of Your Paper.” In Writing an Applied Linguistics Thesis or Dissertation: A Guide to Presenting Empirical Research . John Bitchener, editor. (Basingstoke,UK: Palgrave Macmillan, 2010), pp. 93-105; Tips for Writing a Good Conclusion. Writing@CSU. Colorado State University; Kretchmer, Paul. Twelve Steps to Writing an Effective Conclusion. San Francisco Edit, 2003-2008; Writing Conclusions. Writing Tutorial Services, Center for Innovative Teaching and Learning. Indiana University; Writing: Considering Structure and Organization. Institute for Writing Rhetoric. Dartmouth College.

Writing Tip

Don't Belabor the Obvious!

Avoid phrases like "in conclusion...," "in summary...," or "in closing...." These phrases can be useful, even welcome, in oral presentations. But readers can see by the tell-tale section heading and number of pages remaining that they are reaching the end of your paper. You'll irritate your readers if you belabor the obvious.

Assan, Joseph. "Writing the Conclusion Chapter: The Good, the Bad and the Missing." Liverpool: Development Studies Association (2009): 1-8.

Another Writing Tip

New Insight, Not New Information!

Don't surprise the reader with new information in your conclusion that was never referenced anywhere else in the paper. This why the conclusion rarely has citations to sources. If you have new information to present, add it to the discussion or other appropriate section of the paper. Note that, although no new information is introduced, the conclusion, along with the discussion section, is where you offer your most "original" contributions in the paper; the conclusion is where you describe the value of your research, demonstrate that you understand the material that you’ve presented, and position your findings within the larger context of scholarship on the topic, including describing how your research contributes new insights to that scholarship.

Assan, Joseph. "Writing the Conclusion Chapter: The Good, the Bad and the Missing." Liverpool: Development Studies Association (2009): 1-8; Conclusions. The Writing Center. University of North Carolina.

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How to Write a Conclusion for Research Papers (with Examples)

The conclusion of a research paper is a crucial section that plays a significant role in the overall impact and effectiveness of your research paper. However, this is also the section that typically receives less attention compared to the introduction and the body of the paper. The conclusion serves to provide a concise summary of the key findings, their significance, their implications, and a sense of closure to the study. Discussing how can the findings be applied in real-world scenarios or inform policy, practice, or decision-making is especially valuable to practitioners and policymakers. The research paper conclusion also provides researchers with clear insights and valuable information for their own work, which they can then build on and contribute to the advancement of knowledge in the field.

The research paper conclusion should explain the significance of your findings within the broader context of your field. It restates how your results contribute to the existing body of knowledge and whether they confirm or challenge existing theories or hypotheses. Also, by identifying unanswered questions or areas requiring further investigation, your awareness of the broader research landscape can be demonstrated.

Remember to tailor the research paper conclusion to the specific needs and interests of your intended audience, which may include researchers, practitioners, policymakers, or a combination of these.

Table of Contents

What is a conclusion in a research paper, summarizing conclusion, editorial conclusion, externalizing conclusion, importance of a good research paper conclusion, how to write a conclusion for your research paper, research paper conclusion examples.

• How to write a research paper conclusion with Paperpal? 

Frequently Asked Questions

A conclusion in a research paper is the final section where you summarize and wrap up your research, presenting the key findings and insights derived from your study. The research paper conclusion is not the place to introduce new information or data that was not discussed in the main body of the paper. When working on how to conclude a research paper, remember to stick to summarizing and interpreting existing content. The research paper conclusion serves the following purposes: 1

• Warn readers of the possible consequences of not attending to the problem.
• Recommend specific course(s) of action.
• Restate key ideas to drive home the ultimate point of your research paper.
• Provide a “take-home” message that you want the readers to remember about your study.

Types of conclusions for research papers

In research papers, the conclusion provides closure to the reader. The type of research paper conclusion you choose depends on the nature of your study, your goals, and your target audience. I provide you with three common types of conclusions:

A summarizing conclusion is the most common type of conclusion in research papers. It involves summarizing the main points, reiterating the research question, and restating the significance of the findings. This common type of research paper conclusion is used across different disciplines.

An editorial conclusion is less common but can be used in research papers that are focused on proposing or advocating for a particular viewpoint or policy. It involves presenting a strong editorial or opinion based on the research findings and offering recommendations or calls to action.

An externalizing conclusion is a type of conclusion that extends the research beyond the scope of the paper by suggesting potential future research directions or discussing the broader implications of the findings. This type of conclusion is often used in more theoretical or exploratory research papers.

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The conclusion in a research paper serves several important purposes:

• Offers Implications and Recommendations : Your research paper conclusion is an excellent place to discuss the broader implications of your research and suggest potential areas for further study. It’s also an opportunity to offer practical recommendations based on your findings.
• Provides Closure : A good research paper conclusion provides a sense of closure to your paper. It should leave the reader with a feeling that they have reached the end of a well-structured and thought-provoking research project.
• Leaves a Lasting Impression : Writing a well-crafted research paper conclusion leaves a lasting impression on your readers. It’s your final opportunity to leave them with a new idea, a call to action, or a memorable quote.

Writing a strong conclusion for your research paper is essential to leave a lasting impression on your readers. Here’s a step-by-step process to help you create and know what to put in the conclusion of a research paper: 2

• Research Statement : Begin your research paper conclusion by restating your research statement. This reminds the reader of the main point you’ve been trying to prove throughout your paper. Keep it concise and clear.
• Key Points : Summarize the main arguments and key points you’ve made in your paper. Avoid introducing new information in the research paper conclusion. Instead, provide a concise overview of what you’ve discussed in the body of your paper.
• Address the Research Questions : If your research paper is based on specific research questions or hypotheses, briefly address whether you’ve answered them or achieved your research goals. Discuss the significance of your findings in this context.
• Significance : Highlight the importance of your research and its relevance in the broader context. Explain why your findings matter and how they contribute to the existing knowledge in your field.
• Implications : Explore the practical or theoretical implications of your research. How might your findings impact future research, policy, or real-world applications? Consider the “so what?” question.
• Future Research : Offer suggestions for future research in your area. What questions or aspects remain unanswered or warrant further investigation? This shows that your work opens the door for future exploration.
• Closing Thought : Conclude your research paper conclusion with a thought-provoking or memorable statement. This can leave a lasting impression on your readers and wrap up your paper effectively. Avoid introducing new information or arguments here.
• Proofread and Revise : Carefully proofread your conclusion for grammar, spelling, and clarity. Ensure that your ideas flow smoothly and that your conclusion is coherent and well-structured.

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Remember that a well-crafted research paper conclusion is a reflection of the strength of your research and your ability to communicate its significance effectively. It should leave a lasting impression on your readers and tie together all the threads of your paper. Now you know how to start the conclusion of a research paper and what elements to include to make it impactful, let’s look at a research paper conclusion sample.

How to write a research paper conclusion with Paperpal?

A research paper conclusion is not just a summary of your study, but a synthesis of the key findings that ties the research together and places it in a broader context. A research paper conclusion should be concise, typically around one paragraph in length. However, some complex topics may require a longer conclusion to ensure the reader is left with a clear understanding of the study’s significance. Paperpal, an AI writing assistant trusted by over 800,000 academics globally, can help you write a well-structured conclusion for your research paper. 

• Sign Up or Log In: Create a new Paperpal account or login with your details.  
• Navigate to Features : Once logged in, head over to the features’ side navigation pane. Click on Templates and you’ll find a suite of generative AI features to help you write better, faster.  
• Generate an outline: Under Templates, select ‘Outlines’. Choose ‘Research article’ as your document type.  
• Select your section: Since you’re focusing on the conclusion, select this section when prompted.  
• Choose your field of study: Identifying your field of study allows Paperpal to provide more targeted suggestions, ensuring the relevance of your conclusion to your specific area of research. 
• Provide a brief description of your study: Enter details about your research topic and findings. This information helps Paperpal generate a tailored outline that aligns with your paper’s content. 
• Generate the conclusion outline: After entering all necessary details, click on ‘generate’. Paperpal will then create a structured outline for your conclusion, to help you start writing and build upon the outline.  
• Write your conclusion: Use the generated outline to build your conclusion. The outline serves as a guide, ensuring you cover all critical aspects of a strong conclusion, from summarizing key findings to highlighting the research’s implications. 
• Refine and enhance: Paperpal’s ‘Make Academic’ feature can be particularly useful in the final stages. Select any paragraph of your conclusion and use this feature to elevate the academic tone, ensuring your writing is aligned to the academic journal standards. 

By following these steps, Paperpal not only simplifies the process of writing a research paper conclusion but also ensures it is impactful, concise, and aligned with academic standards. Sign up with Paperpal today and write your research paper conclusion 2x faster .  

The research paper conclusion is a crucial part of your paper as it provides the final opportunity to leave a strong impression on your readers. In the research paper conclusion, summarize the main points of your research paper by restating your research statement, highlighting the most important findings, addressing the research questions or objectives, explaining the broader context of the study, discussing the significance of your findings, providing recommendations if applicable, and emphasizing the takeaway message. The main purpose of the conclusion is to remind the reader of the main point or argument of your paper and to provide a clear and concise summary of the key findings and their implications. All these elements should feature on your list of what to put in the conclusion of a research paper to create a strong final statement for your work.

A strong conclusion is a critical component of a research paper, as it provides an opportunity to wrap up your arguments, reiterate your main points, and leave a lasting impression on your readers. Here are the key elements of a strong research paper conclusion: 1. Conciseness : A research paper conclusion should be concise and to the point. It should not introduce new information or ideas that were not discussed in the body of the paper. 2. Summarization : The research paper conclusion should be comprehensive enough to give the reader a clear understanding of the research’s main contributions. 3 . Relevance : Ensure that the information included in the research paper conclusion is directly relevant to the research paper’s main topic and objectives; avoid unnecessary details. 4 . Connection to the Introduction : A well-structured research paper conclusion often revisits the key points made in the introduction and shows how the research has addressed the initial questions or objectives. 5. Emphasis : Highlight the significance and implications of your research. Why is your study important? What are the broader implications or applications of your findings? 6 . Call to Action : Include a call to action or a recommendation for future research or action based on your findings.

The length of a research paper conclusion can vary depending on several factors, including the overall length of the paper, the complexity of the research, and the specific journal requirements. While there is no strict rule for the length of a conclusion, but it’s generally advisable to keep it relatively short. A typical research paper conclusion might be around 5-10% of the paper’s total length. For example, if your paper is 10 pages long, the conclusion might be roughly half a page to one page in length.

In general, you do not need to include citations in the research paper conclusion. Citations are typically reserved for the body of the paper to support your arguments and provide evidence for your claims. However, there may be some exceptions to this rule: 1. If you are drawing a direct quote or paraphrasing a specific source in your research paper conclusion, you should include a citation to give proper credit to the original author. 2. If your conclusion refers to or discusses specific research, data, or sources that are crucial to the overall argument, citations can be included to reinforce your conclusion’s validity.

The conclusion of a research paper serves several important purposes: 1. Summarize the Key Points 2. Reinforce the Main Argument 3. Provide Closure 4. Offer Insights or Implications 5. Engage the Reader. 6. Reflect on Limitations

Remember that the primary purpose of the research paper conclusion is to leave a lasting impression on the reader, reinforcing the key points and providing closure to your research. It’s often the last part of the paper that the reader will see, so it should be strong and well-crafted.

• Makar, G., Foltz, C., Lendner, M., & Vaccaro, A. R. (2018). How to write effective discussion and conclusion sections. Clinical spine surgery, 31(8), 345-346.
• Bunton, D. (2005). The structure of PhD conclusion chapters.  Journal of English for academic purposes ,  4 (3), 207-224.

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Home » Research Paper Conclusion – Writing Guide and Examples

Research Paper Conclusion – Writing Guide and Examples

Table of Contents

Research Paper Conclusion

Definition:

A research paper conclusion is the final section of a research paper that summarizes the key findings, significance, and implications of the research. It is the writer’s opportunity to synthesize the information presented in the paper, draw conclusions, and make recommendations for future research or actions.

The conclusion should provide a clear and concise summary of the research paper, reiterating the research question or problem, the main results, and the significance of the findings. It should also discuss the limitations of the study and suggest areas for further research.

Parts of Research Paper Conclusion

The parts of a research paper conclusion typically include:

Restatement of the Thesis

The conclusion should begin by restating the thesis statement from the introduction in a different way. This helps to remind the reader of the main argument or purpose of the research.

Summary of Key Findings

The conclusion should summarize the main findings of the research, highlighting the most important results and conclusions. This section should be brief and to the point.

Implications and Significance

In this section, the researcher should explain the implications and significance of the research findings. This may include discussing the potential impact on the field or industry, highlighting new insights or knowledge gained, or pointing out areas for future research.

Limitations and Recommendations

It is important to acknowledge any limitations or weaknesses of the research and to make recommendations for how these could be addressed in future studies. This shows that the researcher is aware of the potential limitations of their work and is committed to improving the quality of research in their field.

Concluding Statement

The conclusion should end with a strong concluding statement that leaves a lasting impression on the reader. This could be a call to action, a recommendation for further research, or a final thought on the topic.

How to Write Research Paper Conclusion

Here are some steps you can follow to write an effective research paper conclusion:

• Restate the research problem or question: Begin by restating the research problem or question that you aimed to answer in your research. This will remind the reader of the purpose of your study.
• Summarize the main points: Summarize the key findings and results of your research. This can be done by highlighting the most important aspects of your research and the evidence that supports them.
• Discuss the implications: Discuss the implications of your findings for the research area and any potential applications of your research. You should also mention any limitations of your research that may affect the interpretation of your findings.
• Provide a conclusion : Provide a concise conclusion that summarizes the main points of your paper and emphasizes the significance of your research. This should be a strong and clear statement that leaves a lasting impression on the reader.
• Offer suggestions for future research: Lastly, offer suggestions for future research that could build on your findings and contribute to further advancements in the field.

Remember that the conclusion should be brief and to the point, while still effectively summarizing the key findings and implications of your research.

Example of Research Paper Conclusion

Here’s an example of a research paper conclusion:

Conclusion :

In conclusion, our study aimed to investigate the relationship between social media use and mental health among college students. Our findings suggest that there is a significant association between social media use and increased levels of anxiety and depression among college students. This highlights the need for increased awareness and education about the potential negative effects of social media use on mental health, particularly among college students.

Despite the limitations of our study, such as the small sample size and self-reported data, our findings have important implications for future research and practice. Future studies should aim to replicate our findings in larger, more diverse samples, and investigate the potential mechanisms underlying the association between social media use and mental health. In addition, interventions should be developed to promote healthy social media use among college students, such as mindfulness-based approaches and social media detox programs.

Overall, our study contributes to the growing body of research on the impact of social media on mental health, and highlights the importance of addressing this issue in the context of higher education. By raising awareness and promoting healthy social media use among college students, we can help to reduce the negative impact of social media on mental health and improve the well-being of young adults.

Purpose of Research Paper Conclusion

The purpose of a research paper conclusion is to provide a summary and synthesis of the key findings, significance, and implications of the research presented in the paper. The conclusion serves as the final opportunity for the writer to convey their message and leave a lasting impression on the reader.

The conclusion should restate the research problem or question, summarize the main results of the research, and explain their significance. It should also acknowledge the limitations of the study and suggest areas for future research or action.

Overall, the purpose of the conclusion is to provide a sense of closure to the research paper and to emphasize the importance of the research and its potential impact. It should leave the reader with a clear understanding of the main findings and why they matter. The conclusion serves as the writer’s opportunity to showcase their contribution to the field and to inspire further research and action.

When to Write Research Paper Conclusion

The conclusion of a research paper should be written after the body of the paper has been completed. It should not be written until the writer has thoroughly analyzed and interpreted their findings and has written a complete and cohesive discussion of the research.

Before writing the conclusion, the writer should review their research paper and consider the key points that they want to convey to the reader. They should also review the research question, hypotheses, and methodology to ensure that they have addressed all of the necessary components of the research.

Once the writer has a clear understanding of the main findings and their significance, they can begin writing the conclusion. The conclusion should be written in a clear and concise manner, and should reiterate the main points of the research while also providing insights and recommendations for future research or action.

Characteristics of Research Paper Conclusion

The characteristics of a research paper conclusion include:

• Clear and concise: The conclusion should be written in a clear and concise manner, summarizing the key findings and their significance.
• Comprehensive: The conclusion should address all of the main points of the research paper, including the research question or problem, the methodology, the main results, and their implications.
• Future-oriented : The conclusion should provide insights and recommendations for future research or action, based on the findings of the research.
• Impressive : The conclusion should leave a lasting impression on the reader, emphasizing the importance of the research and its potential impact.
• Objective : The conclusion should be based on the evidence presented in the research paper, and should avoid personal biases or opinions.
• Unique : The conclusion should be unique to the research paper and should not simply repeat information from the introduction or body of the paper.

Advantages of Research Paper Conclusion

The advantages of a research paper conclusion include:

• Summarizing the key findings : The conclusion provides a summary of the main findings of the research, making it easier for the reader to understand the key points of the study.
• Emphasizing the significance of the research: The conclusion emphasizes the importance of the research and its potential impact, making it more likely that readers will take the research seriously and consider its implications.
• Providing recommendations for future research or action : The conclusion suggests practical recommendations for future research or action, based on the findings of the study.
• Providing closure to the research paper : The conclusion provides a sense of closure to the research paper, tying together the different sections of the paper and leaving a lasting impression on the reader.
• Demonstrating the writer’s contribution to the field : The conclusion provides the writer with an opportunity to showcase their contribution to the field and to inspire further research and action.

Limitations of Research Paper Conclusion

While the conclusion of a research paper has many advantages, it also has some limitations that should be considered, including:

• I nability to address all aspects of the research: Due to the limited space available in the conclusion, it may not be possible to address all aspects of the research in detail.
• Subjectivity : While the conclusion should be objective, it may be influenced by the writer’s personal biases or opinions.
• Lack of new information: The conclusion should not introduce new information that has not been discussed in the body of the research paper.
• Lack of generalizability: The conclusions drawn from the research may not be applicable to other contexts or populations, limiting the generalizability of the study.
• Misinterpretation by the reader: The reader may misinterpret the conclusions drawn from the research, leading to a misunderstanding of the findings.

About the author

Muhammad Hassan

Researcher, Academic Writer, Web developer

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• How to Write Discussions and Conclusions

The discussion section contains the results and outcomes of a study. An effective discussion informs readers what can be learned from your experiment and provides context for the results.

What makes an effective discussion?

When you’re ready to write your discussion, you’ve already introduced the purpose of your study and provided an in-depth description of the methodology. The discussion informs readers about the larger implications of your study based on the results. Highlighting these implications while not overstating the findings can be challenging, especially when you’re submitting to a journal that selects articles based on novelty or potential impact. Regardless of what journal you are submitting to, the discussion section always serves the same purpose: concluding what your study results actually mean.

A successful discussion section puts your findings in context. It should include:

• the results of your research,
• a discussion of related research, and
• a comparison between your results and initial hypothesis.

Tip: Not all journals share the same naming conventions.

You can apply the advice in this article to the conclusion, results or discussion sections of your manuscript.

Our Early Career Researcher community tells us that the conclusion is often considered the most difficult aspect of a manuscript to write. To help, this guide provides questions to ask yourself, a basic structure to model your discussion off of and examples from published manuscripts. 

Questions to ask yourself:

• Was my hypothesis correct?
• If my hypothesis is partially correct or entirely different, what can be learned from the results? 
• How do the conclusions reshape or add onto the existing knowledge in the field? What does previous research say about the topic? 
• Why are the results important or relevant to your audience? Do they add further evidence to a scientific consensus or disprove prior studies? 
• How can future research build on these observations? What are the key experiments that must be done? 
• What is the “take-home” message you want your reader to leave with?

How to structure a discussion

Trying to fit a complete discussion into a single paragraph can add unnecessary stress to the writing process. If possible, you’ll want to give yourself two or three paragraphs to give the reader a comprehensive understanding of your study as a whole. Here’s one way to structure an effective discussion:

Writing Tips

While the above sections can help you brainstorm and structure your discussion, there are many common mistakes that writers revert to when having difficulties with their paper. Writing a discussion can be a delicate balance between summarizing your results, providing proper context for your research and avoiding introducing new information. Remember that your paper should be both confident and honest about the results! 

• Read the journal’s guidelines on the discussion and conclusion sections. If possible, learn about the guidelines before writing the discussion to ensure you’re writing to meet their expectations. 
• Begin with a clear statement of the principal findings. This will reinforce the main take-away for the reader and set up the rest of the discussion. 
• Explain why the outcomes of your study are important to the reader. Discuss the implications of your findings realistically based on previous literature, highlighting both the strengths and limitations of the research. 
• State whether the results prove or disprove your hypothesis. If your hypothesis was disproved, what might be the reasons? 
• Introduce new or expanded ways to think about the research question. Indicate what next steps can be taken to further pursue any unresolved questions. 
• If dealing with a contemporary or ongoing problem, such as climate change, discuss possible consequences if the problem is avoided. 
• Be concise. Adding unnecessary detail can distract from the main findings. 

Don’t

• Rewrite your abstract. Statements with “we investigated” or “we studied” generally do not belong in the discussion. 
• Include new arguments or evidence not previously discussed. Necessary information and evidence should be introduced in the main body of the paper. 
• Apologize. Even if your research contains significant limitations, don’t undermine your authority by including statements that doubt your methodology or execution. 
• Shy away from speaking on limitations or negative results. Including limitations and negative results will give readers a complete understanding of the presented research. Potential limitations include sources of potential bias, threats to internal or external validity, barriers to implementing an intervention and other issues inherent to the study design. 
• Overstate the importance of your findings. Making grand statements about how a study will fully resolve large questions can lead readers to doubt the success of the research. 

Snippets of Effective Discussions:

Consumer-based actions to reduce plastic pollution in rivers: A multi-criteria decision analysis approach

Identifying reliable indicators of fitness in polar bears

• How to Write a Great Title
• How to Write an Abstract
• How to Write Your Methods
• How to Report Statistics
• How to Edit Your Work

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How to write a strong conclusion for your research paper

Last updated

17 February 2024

Reviewed by

Writing a research paper is a chance to share your knowledge and hypothesis. It's an opportunity to demonstrate your many hours of research and prove your ability to write convincingly.

Ideally, by the end of your research paper, you'll have brought your readers on a journey to reach the conclusions you've pre-determined. However, if you don't stick the landing with a good conclusion, you'll risk losing your reader’s trust.

Writing a strong conclusion for your research paper involves a few important steps, including restating the thesis and summing up everything properly.

Find out what to include and what to avoid, so you can effectively demonstrate your understanding of the topic and prove your expertise.

• Why is a good conclusion important?

A good conclusion can cement your paper in the reader’s mind. Making a strong impression in your introduction can draw your readers in, but it's the conclusion that will inspire them.

• What to include in a research paper conclusion

There are a few specifics you should include in your research paper conclusion. Offer your readers some sense of urgency or consequence by pointing out why they should care about the topic you have covered. Discuss any common problems associated with your topic and provide suggestions as to how these problems can be solved or addressed.

The conclusion should include a restatement of your initial thesis. Thesis statements are strengthened after you’ve presented supporting evidence (as you will have done in the paper), so make a point to reintroduce it at the end.

Finally, recap the main points of your research paper, highlighting the key takeaways you want readers to remember. If you've made multiple points throughout the paper, refer to the ones with the strongest supporting evidence.

• Steps for writing a research paper conclusion

Many writers find the conclusion the most challenging part of any research project . By following these three steps, you'll be prepared to write a conclusion that is effective and concise.

• Step 1: Restate the problem

Always begin by restating the research problem in the conclusion of a research paper. This serves to remind the reader of your hypothesis and refresh them on the main point of the paper. 

When restating the problem, take care to avoid using exactly the same words you employed earlier in the paper.

• Step 2: Sum up the paper

After you've restated the problem, sum up the paper by revealing your overall findings. The method for this differs slightly, depending on whether you're crafting an argumentative paper or an empirical paper.

Argumentative paper: Restate your thesis and arguments

Argumentative papers involve introducing a thesis statement early on. In crafting the conclusion for an argumentative paper, always restate the thesis, outlining the way you've developed it throughout the entire paper.

It might be appropriate to mention any counterarguments in the conclusion, so you can demonstrate how your thesis is correct or how the data best supports your main points.

Empirical paper: Summarize research findings

Empirical papers break down a series of research questions. In your conclusion, discuss the findings your research revealed, including any information that surprised you.

Be clear about the conclusions you reached, and explain whether or not you expected to arrive at these particular ones.

• Step 3: Discuss the implications of your research

Argumentative papers and empirical papers also differ in this part of a research paper conclusion. Here are some tips on crafting conclusions for argumentative and empirical papers.

Argumentative paper: Powerful closing statement

In an argumentative paper, you'll have spent a great deal of time expressing the opinions you formed after doing a significant amount of research. Make a strong closing statement in your argumentative paper's conclusion to share the significance of your work.

You can outline the next steps through a bold call to action, or restate how powerful your ideas turned out to be.

Empirical paper: Directions for future research

Empirical papers are broader in scope. They usually cover a variety of aspects and can include several points of view.

To write a good conclusion for an empirical paper, suggest the type of research that could be done in the future, including methods for further investigation or outlining ways other researchers might proceed.

If you feel your research had any limitations, even if they were outside your control, you could mention these in your conclusion.

After you finish outlining your conclusion, ask someone to read it and offer feedback. In any research project you're especially close to, it can be hard to identify problem areas. Having a close friend or someone whose opinion you value read the research paper and provide honest feedback can be invaluable. Take note of any suggested edits and consider incorporating them into your paper if they make sense.

• Things to avoid in a research paper conclusion

Keep these aspects to avoid in mind as you're writing your conclusion and refer to them after you've created an outline.

Dry summary

Writing a memorable, succinct conclusion is arguably more important than a strong introduction. Take care to avoid just rephrasing your main points, and don't fall into the trap of repeating dry facts or citations.

You can provide a new perspective for your readers to think about or contextualize your research. Either way, make the conclusion vibrant and interesting, rather than a rote recitation of your research paper’s highlights.

Clichéd or generic phrasing

Your research paper conclusion should feel fresh and inspiring. Avoid generic phrases like "to sum up" or "in conclusion." These phrases tend to be overused, especially in an academic context and might turn your readers off.

The conclusion also isn't the time to introduce colloquial phrases or informal language. Retain a professional, confident tone consistent throughout your paper’s conclusion so it feels exciting and bold.

New data or evidence

While you should present strong data throughout your paper, the conclusion isn't the place to introduce new evidence. This is because readers are engaged in actively learning as they read through the body of your paper.

By the time they reach the conclusion, they will have formed an opinion one way or the other (hopefully in your favor!). Introducing new evidence in the conclusion will only serve to surprise or frustrate your reader.

Ignoring contradictory evidence

If your research reveals contradictory evidence, don't ignore it in the conclusion. This will damage your credibility as an expert and might even serve to highlight the contradictions.

Be as transparent as possible and admit to any shortcomings in your research, but don't dwell on them for too long.

Ambiguous or unclear resolutions

The point of a research paper conclusion is to provide closure and bring all your ideas together. You should wrap up any arguments you introduced in the paper and tie up any loose ends, while demonstrating why your research and data are strong.

Use direct language in your conclusion and avoid ambiguity. Even if some of the data and sources you cite are inconclusive or contradictory, note this in your conclusion to come across as confident and trustworthy.

• Examples of research paper conclusions

Your research paper should provide a compelling close to the paper as a whole, highlighting your research and hard work. While the conclusion should represent your unique style, these examples offer a starting point:

Ultimately, the data we examined all point to the same conclusion: Encouraging a good work-life balance improves employee productivity and benefits the company overall. The research suggests that when employees feel their personal lives are valued and respected by their employers, they are more likely to be productive when at work. In addition, company turnover tends to be reduced when employees have a balance between their personal and professional lives. While additional research is required to establish ways companies can support employees in creating a stronger work-life balance, it's clear the need is there.

Social media is a primary method of communication among young people. As we've seen in the data presented, most young people in high school use a variety of social media applications at least every hour, including Instagram and Facebook. While social media is an avenue for connection with peers, research increasingly suggests that social media use correlates with body image issues. Young girls with lower self-esteem tend to use social media more often than those who don't log onto social media apps every day. As new applications continue to gain popularity, and as more high school students are given smartphones, more research will be required to measure the effects of prolonged social media use.

What are the different kinds of research paper conclusions?

There are no formal types of research paper conclusions. Ultimately, the conclusion depends on the outline of your paper and the type of research you’re presenting. While some experts note that research papers can end with a new perspective or commentary, most papers should conclude with a combination of both. The most important aspect of a good research paper conclusion is that it accurately represents the body of the paper.

Can I present new arguments in my research paper conclusion?

Research paper conclusions are not the place to introduce new data or arguments. The body of your paper is where you should share research and insights, where the reader is actively absorbing the content. By the time a reader reaches the conclusion of the research paper, they should have formed their opinion. Introducing new arguments in the conclusion can take a reader by surprise, and not in a positive way. It might also serve to frustrate readers.

How long should a research paper conclusion be?

There's no set length for a research paper conclusion. However, it's a good idea not to run on too long, since conclusions are supposed to be succinct. A good rule of thumb is to keep your conclusion around 5 to 10 percent of the paper's total length. If your paper is 10 pages, try to keep your conclusion under one page.

What should I include in a research paper conclusion?

A good research paper conclusion should always include a sense of urgency, so the reader can see how and why the topic should matter to them. You can also note some recommended actions to help fix the problem and some obstacles they might encounter. A conclusion should also remind the reader of the thesis statement, along with the main points you covered in the paper. At the end of the conclusion, add a powerful closing statement that helps cement the paper in the mind of the reader.

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Conclusions

What this handout is about.

This handout will explain the functions of conclusions, offer strategies for writing effective ones, help you evaluate conclusions you’ve drafted, and suggest approaches to avoid.

About conclusions

Introductions and conclusions can be difficult to write, but they’re worth investing time in. They can have a significant influence on a reader’s experience of your paper.

Just as your introduction acts as a bridge that transports your readers from their own lives into the “place” of your analysis, your conclusion can provide a bridge to help your readers make the transition back to their daily lives. Such a conclusion will help them see why all your analysis and information should matter to them after they put the paper down.

Your conclusion is your chance to have the last word on the subject. The conclusion allows you to have the final say on the issues you have raised in your paper, to synthesize your thoughts, to demonstrate the importance of your ideas, and to propel your reader to a new view of the subject. It is also your opportunity to make a good final impression and to end on a positive note.

Your conclusion can go beyond the confines of the assignment. The conclusion pushes beyond the boundaries of the prompt and allows you to consider broader issues, make new connections, and elaborate on the significance of your findings.

Your conclusion should make your readers glad they read your paper. Your conclusion gives your reader something to take away that will help them see things differently or appreciate your topic in personally relevant ways. It can suggest broader implications that will not only interest your reader, but also enrich your reader’s life in some way. It is your gift to the reader.

Strategies for writing an effective conclusion

One or more of the following strategies may help you write an effective conclusion:

• Play the “So What” Game. If you’re stuck and feel like your conclusion isn’t saying anything new or interesting, ask a friend to read it with you. Whenever you make a statement from your conclusion, ask the friend to say, “So what?” or “Why should anybody care?” Then ponder that question and answer it. Here’s how it might go: You: Basically, I’m just saying that education was important to Douglass. Friend: So what? You: Well, it was important because it was a key to him feeling like a free and equal citizen. Friend: Why should anybody care? You: That’s important because plantation owners tried to keep slaves from being educated so that they could maintain control. When Douglass obtained an education, he undermined that control personally. You can also use this strategy on your own, asking yourself “So What?” as you develop your ideas or your draft.
• Return to the theme or themes in the introduction. This strategy brings the reader full circle. For example, if you begin by describing a scenario, you can end with the same scenario as proof that your essay is helpful in creating a new understanding. You may also refer to the introductory paragraph by using key words or parallel concepts and images that you also used in the introduction.
• Synthesize, don’t summarize. Include a brief summary of the paper’s main points, but don’t simply repeat things that were in your paper. Instead, show your reader how the points you made and the support and examples you used fit together. Pull it all together.
• Include a provocative insight or quotation from the research or reading you did for your paper.
• Propose a course of action, a solution to an issue, or questions for further study. This can redirect your reader’s thought process and help them to apply your info and ideas to their own life or to see the broader implications.
• Point to broader implications. For example, if your paper examines the Greensboro sit-ins or another event in the Civil Rights Movement, you could point out its impact on the Civil Rights Movement as a whole. A paper about the style of writer Virginia Woolf could point to her influence on other writers or on later feminists.

Strategies to avoid

• Beginning with an unnecessary, overused phrase such as “in conclusion,” “in summary,” or “in closing.” Although these phrases can work in speeches, they come across as wooden and trite in writing.
• Stating the thesis for the very first time in the conclusion.
• Introducing a new idea or subtopic in your conclusion.
• Ending with a rephrased thesis statement without any substantive changes.
• Making sentimental, emotional appeals that are out of character with the rest of an analytical paper.
• Including evidence (quotations, statistics, etc.) that should be in the body of the paper.

Four kinds of ineffective conclusions

• The “That’s My Story and I’m Sticking to It” Conclusion. This conclusion just restates the thesis and is usually painfully short. It does not push the ideas forward. People write this kind of conclusion when they can’t think of anything else to say. Example: In conclusion, Frederick Douglass was, as we have seen, a pioneer in American education, proving that education was a major force for social change with regard to slavery.
• The “Sherlock Holmes” Conclusion. Sometimes writers will state the thesis for the very first time in the conclusion. You might be tempted to use this strategy if you don’t want to give everything away too early in your paper. You may think it would be more dramatic to keep the reader in the dark until the end and then “wow” them with your main idea, as in a Sherlock Holmes mystery. The reader, however, does not expect a mystery, but an analytical discussion of your topic in an academic style, with the main argument (thesis) stated up front. Example: (After a paper that lists numerous incidents from the book but never says what these incidents reveal about Douglass and his views on education): So, as the evidence above demonstrates, Douglass saw education as a way to undermine the slaveholders’ power and also an important step toward freedom.
• The “America the Beautiful”/”I Am Woman”/”We Shall Overcome” Conclusion. This kind of conclusion usually draws on emotion to make its appeal, but while this emotion and even sentimentality may be very heartfelt, it is usually out of character with the rest of an analytical paper. A more sophisticated commentary, rather than emotional praise, would be a more fitting tribute to the topic. Example: Because of the efforts of fine Americans like Frederick Douglass, countless others have seen the shining beacon of light that is education. His example was a torch that lit the way for others. Frederick Douglass was truly an American hero.
• The “Grab Bag” Conclusion. This kind of conclusion includes extra information that the writer found or thought of but couldn’t integrate into the main paper. You may find it hard to leave out details that you discovered after hours of research and thought, but adding random facts and bits of evidence at the end of an otherwise-well-organized essay can just create confusion. Example: In addition to being an educational pioneer, Frederick Douglass provides an interesting case study for masculinity in the American South. He also offers historians an interesting glimpse into slave resistance when he confronts Covey, the overseer. His relationships with female relatives reveal the importance of family in the slave community.

Works consulted

We consulted these works while writing this handout. This is not a comprehensive list of resources on the handout’s topic, and we encourage you to do your own research to find additional publications. Please do not use this list as a model for the format of your own reference list, as it may not match the citation style you are using. For guidance on formatting citations, please see the UNC Libraries citation tutorial . We revise these tips periodically and welcome feedback.

Douglass, Frederick. 1995. Narrative of the Life of Frederick Douglass, an American Slave, Written by Himself. New York: Dover.

Hamilton College. n.d. “Conclusions.” Writing Center. Accessed June 14, 2019. https://www.hamilton.edu//academics/centers/writing/writing-resources/conclusions .

Holewa, Randa. 2004. “Strategies for Writing a Conclusion.” LEO: Literacy Education Online. Last updated February 19, 2004. https://leo.stcloudstate.edu/acadwrite/conclude.html.

You may reproduce it for non-commercial use if you use the entire handout and attribute the source: The Writing Center, University of North Carolina at Chapel Hill

Make a Gift

In a short paper—even a research paper—you don’t need to provide an exhaustive summary as part of your conclusion. But you do need to make some kind of transition between your final body paragraph and your concluding paragraph. This may come in the form of a few sentences of summary. Or it may come in the form of a sentence that brings your readers back to your thesis or main idea and reminds your readers where you began and how far you have traveled.

So, for example, in a paper about the relationship between ADHD and rejection sensitivity, Vanessa Roser begins by introducing readers to the fact that researchers have studied the relationship between the two conditions and then provides her explanation of that relationship. Here’s her thesis: “While socialization may indeed be an important factor in RS, I argue that individuals with ADHD may also possess a neurological predisposition to RS that is exacerbated by the differing executive and emotional regulation characteristic of ADHD.”

In her final paragraph, Roser reminds us of where she started by echoing her thesis: “This literature demonstrates that, as with many other conditions, ADHD and RS share a delicately intertwined pattern of neurological similarities that is rooted in the innate biology of an individual’s mind, a connection that cannot be explained in full by the behavioral mediation hypothesis.”  

Highlight the “so what”  

At the beginning of your paper, you explain to your readers what’s at stake—why they should care about the argument you’re making. In your conclusion, you can bring readers back to those stakes by reminding them why your argument is important in the first place. You can also draft a few sentences that put those stakes into a new or broader context.

In the conclusion to her paper about ADHD and RS, Roser echoes the stakes she established in her introduction—that research into connections between ADHD and RS has led to contradictory results, raising questions about the “behavioral mediation hypothesis.”

She writes, “as with many other conditions, ADHD and RS share a delicately intertwined pattern of neurological similarities that is rooted in the innate biology of an individual’s mind, a connection that cannot be explained in full by the behavioral mediation hypothesis.”  

Leave your readers with the “now what”  

After the “what” and the “so what,” you should leave your reader with some final thoughts. If you have written a strong introduction, your readers will know why you have been arguing what you have been arguing—and why they should care. And if you’ve made a good case for your thesis, then your readers should be in a position to see things in a new way, understand new questions, or be ready for something that they weren’t ready for before they read your paper.

In her conclusion, Roser offers two “now what” statements. First, she explains that it is important to recognize that the flawed behavioral mediation hypothesis “seems to place a degree of fault on the individual. It implies that individuals with ADHD must have elicited such frequent or intense rejection by virtue of their inadequate social skills, erasing the possibility that they may simply possess a natural sensitivity to emotion.” She then highlights the broader implications for treatment of people with ADHD, noting that recognizing the actual connection between rejection sensitivity and ADHD “has profound implications for understanding how individuals with ADHD might best be treated in educational settings, by counselors, family, peers, or even society as a whole.”

To find your own “now what” for your essay’s conclusion, try asking yourself these questions:

• What can my readers now understand, see in a new light, or grapple with that they would not have understood in the same way before reading my paper? Are we a step closer to understanding a larger phenomenon or to understanding why what was at stake is so important?  
• What questions can I now raise that would not have made sense at the beginning of my paper? Questions for further research? Other ways that this topic could be approached?  
• Are there other applications for my research? Could my questions be asked about different data in a different context? Could I use my methods to answer a different question?  
• What action should be taken in light of this argument? What action do I predict will be taken or could lead to a solution?  
• What larger context might my argument be a part of?  

What to avoid in your conclusion  

• a complete restatement of all that you have said in your paper.  
• a substantial counterargument that you do not have space to refute; you should introduce counterarguments before your conclusion.  
• an apology for what you have not said. If you need to explain the scope of your paper, you should do this sooner—but don’t apologize for what you have not discussed in your paper.  
• fake transitions like “in conclusion” that are followed by sentences that aren’t actually conclusions. (“In conclusion, I have now demonstrated that my thesis is correct.”)
• picture_as_pdf Conclusions

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How to Write a Conclusion for a Research Paper

3-minute read

• 29th August 2023

If you’re writing a research paper, the conclusion is your opportunity to summarize your findings and leave a lasting impression on your readers. In this post, we’ll take you through how to write an effective conclusion for a research paper and how you can:

·   Reword your thesis statement

·   Highlight the significance of your research

·   Discuss limitations

·   Connect to the introduction

·   End with a thought-provoking statement

Rewording Your Thesis Statement

Begin your conclusion by restating your thesis statement in a way that is slightly different from the wording used in the introduction. Avoid presenting new information or evidence in your conclusion. Just summarize the main points and arguments of your essay and keep this part as concise as possible. Remember that you’ve already covered the in-depth analyses and investigations in the main body paragraphs of your essay, so it’s not necessary to restate these details in the conclusion.

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Highlighting the Significance of Your Research

The conclusion is a good place to emphasize the implications of your research . Avoid ambiguous or vague language such as “I think” or “maybe,” which could weaken your position. Clearly explain why your research is significant and how it contributes to the broader field of study.

Here’s an example from a (fictional) study on the impact of social media on mental health:

Discussing Limitations

Although it’s important to emphasize the significance of your study, you can also use the conclusion to briefly address any limitations you discovered while conducting your research, such as time constraints or a shortage of resources. Doing this demonstrates a balanced and honest approach to your research.

Connecting to the Introduction

In your conclusion, you can circle back to your introduction , perhaps by referring to a quote or anecdote you discussed earlier. If you end your paper on a similar note to how you began it, you will create a sense of cohesion for the reader and remind them of the meaning and significance of your research.

Ending With a Thought-Provoking Statement

Consider ending your paper with a thought-provoking and memorable statement that relates to the impact of your research questions or hypothesis. This statement can be a call to action, a philosophical question, or a prediction for the future (positive or negative). Here’s an example that uses the same topic as above (social media and mental health):

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Organizing Academic Research Papers: 9. The Conclusion

• Purpose of Guide
• Design Flaws to Avoid
• Glossary of Research Terms
• Narrowing a Topic Idea
• Broadening a Topic Idea
• Extending the Timeliness of a Topic Idea
• Academic Writing Style
• Choosing a Title
• Making an Outline
• Paragraph Development
• Executive Summary
• Background Information
• The Research Problem/Question
• Theoretical Framework
• Citation Tracking
• Content Alert Services
• Evaluating Sources
• Primary Sources
• Secondary Sources
• Tertiary Sources
• What Is Scholarly vs. Popular?
• Qualitative Methods
• Quantitative Methods
• Using Non-Textual Elements
• Limitations of the Study
• Common Grammar Mistakes
• Avoiding Plagiarism
• Footnotes or Endnotes?
• Further Readings
• Annotated Bibliography
• Dealing with Nervousness
• Using Visual Aids
• Grading Someone Else's Paper
• How to Manage Group Projects
• Multiple Book Review Essay
• Reviewing Collected Essays
• About Informed Consent
• Writing Field Notes
• Writing a Policy Memo
• Writing a Research Proposal
• Acknowledgements

The conclusion is intended to help the reader understand why your research should matter to them after they have finished reading the paper. A conclusion is not merely a summary of your points or a re-statement of your research problem but a synthesis of key points. For most essays, one well-developed paragraph is sufficient for a conclusion, although in some cases, a two-or-three paragraph conclusion may be required.

Importance of a Good Conclusion

A well-written conclusion provides you with several important opportunities to demonstrate your overall understanding of the research problem to the reader. These include:

• Presenting the last word on the issues you raised in your paper . Just as the introduction gives a first impression to your reader, the conclusion offers a chance to leave a lasting impression. Do this, for example, by highlighting key points in your analysis or findings.
• Summarizing your thoughts and conveying the larger implications of your study . The conclusion is an opportunity to succinctly answer the "so what?" question by placing the study within the context of past research about the topic you've investigated.
• Demonstrating the importance of your ideas . Don't be shy. The conclusion offers you a chance to elaborate on the significance of your findings.
• Introducing possible new or expanded ways of thinking about the research problem . This does not refer to introducing new information [which should be avoided], but to offer new insight and creative approaches for framing/contextualizing the research problem based on the results of your study.

Conclusions . The Writing Center. University of North Carolina; Kretchmer, Paul. Twelve Steps to Writing an Effective Conclusion . San Francisco Edit, 2003-2008.

Structure and Writing Style

https://writing.wisc.edu/wp-content/uploads/sites/535/2018/07/conclusions_uwmadison_writingcenter_aug2012.pdf I.  General Rules

When writing the conclusion to your paper, follow these general rules:

• State your conclusions in clear, simple language.
• Do not simply reiterate your results or the discussion.
• Indicate opportunities for future research, as long as you haven't already done so in the discussion section of your paper.

The function of your paper's conclusion is to restate the main argument . It reminds the reader of the strengths of your main argument(s) and reiterates the most important evidence supporting those argument(s). Make sure, however, that your conclusion is not simply a repetitive summary of the findings because this reduces the impact of the argument(s) you have developed in your essay.

Consider the following points to help ensure your conclusion is appropriate:

• If the argument or point of your paper is complex, you may need to summarize the argument for your reader.
• If, prior to your conclusion, you have not yet explained the significance of your findings or if you are proceeding inductively, use the end of your paper to describe your main points and explain their significance.
• Move from a detailed to a general level of consideration that returns the topic to the context provided by the introduction or within a new context that emerges from the data.

The conclusion also provides a place for you to persuasively and succinctly restate your research problem, given that the reader has now been presented with all the information about the topic . Depending on the discipline you are writing in, the concluding paragraph may contain your reflections on the evidence presented, or on the essay's central research problem. However, the nature of being introspective about the research you have done will depend on the topic and whether your professor wants you to express your observations in this way.

NOTE : Don't delve into idle speculation. Being introspective means looking within yourself as an author to try and understand an issue more deeply not to guess at possible outcomes.

II.  Developing a Compelling Conclusion

Strategies to help you move beyond merely summarizing the key points of your research paper may include any of the following.

• If your essay deals with a contemporary problem, warn readers of the possible consequences of not attending to the problem.
• Recommend a specific course or courses of action.
• Cite a relevant quotation or expert opinion to lend authority to the conclusion you have reached [a good place to look is research from your literature review].
• Restate a key statistic, fact, or visual image to drive home the ultimate point of your paper.
• If your discipline encourages personal reflection, illustrate your concluding point with a relevant narrative drawn from your own life experiences.
• Return to an anecdote, an example, or a quotation that you introduced in your introduction, but add further insight that is derived from the findings of your study; use your interpretation of results to reframe it in new ways.
• Provide a "take-home" message in the form of a strong, succient statement that you want the reader to remember about your study.

III. Problems to Avoid Failure to be concise The conclusion section should be concise and to the point. Conclusions that are too long often have unnecessary detail. The conclusion section is not the place for details about your methodology or results. Although you should give a summary of what was learned from your research, this summary should be relatively brief, since the emphasis in the conclusion is on the implications, evaluations, insights, etc. that you make. Failure to comment on larger, more significant issues In the introduction, your task was to move from general [the field of study] to specific [your research problem]. However, in the conclusion, your task is to move from specific [your research problem] back to general [your field, i.e., how your research contributes new understanding or fills an important gap in the literature]. In other words, the conclusion is where you place your research within a larger context. Failure to reveal problems and negative results Negative aspects of the research process should never be ignored. Problems, drawbacks, and challenges encountered during your study should be included as a way of qualifying your overall conclusions. If you encountered negative results [findings that are validated outside the research context in which they were generated], you must report them in the results section of your paper. In the conclusion, use the negative results as an opportunity to explain how they provide information on which future research can be based. Failure to provide a clear summary of what was learned In order to be able to discuss how your research fits back into your field of study [and possibly the world at large], you need to summarize it briefly and directly. Often this element of your conclusion is only a few sentences long. Failure to match the objectives of your research Often research objectives change while the research is being carried out. This is not a problem unless you forget to go back and refine your original objectives in your introduction, as these changes emerge they must be documented so that they accurately reflect what you were trying to accomplish in your research [not what you thought you might accomplish when you began].

Resist the urge to apologize If you've immersed yourself in studying the research problem, you now know a good deal about it, perhaps even more than your professor! Nevertheless, by the time you have finished writing, you may be having some doubts about what you have produced. Repress those doubts!  Don't undermine your authority by saying something like, "This is just one approach to examining this problem; there may be other, much better approaches...."

Concluding Paragraphs. College Writing Center at Meramec. St. Louis Community College; Conclusions . The Writing Center. University of North Carolina; Conclusions . The Writing Lab and The OWL. Purdue University; Freedman, Leora  and Jerry Plotnick. Introductions and Conclusions . The Lab Report. University College Writing Centre. University of Toronto; Leibensperger, Summer. Draft Your Conclusion. Academic Center, the University of Houston-Victoria, 2003; Make Your Last Words Count . The Writer’s Handbook. Writing Center. University of Wisconsin, Madison; Tips for Writing a Good Conclusion . Writing@CSU. Colorado State University; Kretchmer, Paul. Twelve Steps to Writing an Effective Conclusion . San Francisco Edit, 2003-2008; Writing Conclusions . Writing Tutorial Services, Center for Innovative Teaching and Learning. Indiana University; Writing: Considering Structure and Organization . Institute for Writing Rhetoric. Dartmouth College.

Writing Tip

Don't Belabor the Obvious!

Avoid phrases like "in conclusion...," "in summary...," or "in closing...." These phrases can be useful, even welcome, in oral presentations. But readers can see by the tell-tale section heading and number of pages remaining to read, when an essay is about to end. You'll irritate your readers if you belabor the obvious.

Another Writing Tip

New Insight, Not New Information!

Don't surprise the reader with new information in your Conclusion that was never referenced anywhere else in the paper. If you have new information to present, add it to the Discussion or other appropriate section of the paper.  Note that, although no actual new information is introduced, the conclusion is where you offer your most "original" contributions in the paper; it's where you describe the value of your research, demonstrate your understanding of the material that you’ve presented, and locate your findings within the larger context of scholarship on the topic.

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The Conclusion: How to End a Scientific Report in Style

• First Online: 26 April 2023

Cite this chapter

• Siew Mei Wu 3 ,
• Kooi Cheng Lee 3 &
• Eric Chun Yong Chan 4  

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Sometimes students have the mistaken belief that the conclusion of a scientific report is just a perfunctory ending that repeats what was presented in the main sections of the report. However, impactful conclusions fulfill a rhetorical function. Besides giving a closing summary, the conclusion reflects the significance of what has been uncovered and how this is connected to a broader issue. At the very least, the conclusion of a scientific report should leave the reader with a new perspective of the research area and something to think about.

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Goh, Z.-H., Tee, J. K., &amp; Ho, H. K. (2020). An Evaluation of the in vitro roles and mechanisms of silibinin in reducing pyrazinamide and isoniazid-induced hepatocellular damage. International Journal of Molecular Sciences, 21 , 3714–3734. https://doi.org/10.3390/ijms21103714

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Swales, J. M., &amp; Feak, C. B. (2012). Academic writing for graduate students (3rd ed.). University of Michigan Press.

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Appendix 1: Tutorial Notes for Conclusion Activity

1.1 learning outcomes.

At the end of the tutorial, you should be able to:

Identify and demonstrate understanding of the roles of Conclusion section of research reports

Analyze the rhetorical moves of Conclusion and apply them effectively in research reports

1.2 Introduction

The Conclusion of a paper is a closing summary of what the report is about. The key role of a Conclusion is to provide a reflection on what has been uncovered during the course of the study and to reflect on the significance of what has been learned (Craswell &amp; Poore, 2012). It should show the readers why all the analysis and information matters.

Besides having a final say on the issues in the report, a Conclusion allows the writer to do the following:

Demonstrate the importance of ideas presented through a synthesis of thoughts

Consider broader issues, make new connections, and elaborate on the significance of the findings

Propel the reader to a new view of the subject

Make a good final impression

End the paper on a positive note

(University of North Carolina at Chapel Hill, 2019)

In other words, a Conclusion gives the readers something to take away that will help them see things differently or appreciate the topic in new ways. It can suggest broader implications that will not only interest the readers, but also enrich their knowledge (Craswell &amp; Poore, 2012), and leave them with something interesting to think about (University of North Carolina at Chapel Hill, 2019).

1.3 About the Conclusion Section

In most universities, undergraduate students, especially those in the last year of their programs, are required to document their research work in the form of a research report. The process of taking what you have done in the lab or from systematic review, and writing it for your academic colleagues is a highly structured activity that stretches and challenges the mind. Overall, a research paper should appeal to the academic community for whom you are writing and should cause the reader to want to know more about your research.

As an undergraduate student in your discipline, you have the advantage of being engaged in a niche area of research. As such, your research is current and will most likely be of interest to scholars in your community.

A typical research paper has the following main sections: introduction, methods, results, discussion, and conclusion. The other front and back matters of a research paper are the title, abstract, acknowledgments, and reference list. This structure is commonly adopted and accepted in the scientific fields. The research report starts with a general idea. The report then leads the reader to a discussion on a specific research area. It then ends with applicability to a bigger area. The last section, Conclusion, is the focus of this lesson.

The rhetorical moves of a Conclusion reflect its roles (see Fig. 54.1 ). It starts by reminding the reader of what is presented in the Introduction. For example, if a problem is described in the Introduction, that same problem can be revisited in the Conclusion to provide evidence that the report is helpful in creating a new understanding of the problem. The writer can also refer to the Introduction by using keywords or parallel concepts that were presented there.

Rhetorical moves of Conclusion (the University of North Carolina at Chapel Hill Writing Center,2019)

Next is a synthesis and not a summary of the outcomes of the study. Ideas should not simply be repeated as they were in the earlier parts of the report. The writer must show how the points made, and the support and examples that were given, fit together.

In terms of limitations, if it is not already mentioned in the Discussion section, the writer should acknowledge the weaknesses and shortcomings in the design and/or conduct of the study.

Finally, in connecting to the wider context, the writer should propose a course of action, a solution to an issue, or pose questions for further study. This can redirect readers’ thoughts and help them apply the information and ideas in the study to their own research context or to see the broader implications of the study.

1.4 Linguistic Features of the Conclusion Section

In terms of linguistic features, the use of tense in the Conclusion section is primarily present where the writer’s voice, position, and interpretation are prominent. This is followed by the use of the future tense in sharing what is ahead and some use of past when referring to the study that was done. As summarized by Swales and Feak (2012), Table 54.1 presents the frequency of use of the present tense and past tense in a research report.

1.5 Writing the Conclusion Section

Often, writing a Conclusion is not as easy as it first seems. Using the Question and Answer approach, below is a description of what is usually included in the Conclusion section.

How long should the Conclusion be?

One or two paragraphs comprising 1 sentence summarizing what the paper was about

Two to three sentences summarizing and synthesizing the key findings related to the thesis or objectives of the study

One sentence on limitations (if not in Discussion)

One to two sentences highlighting the significance and implications

One sentence on potential directions for further research

Should the objective be referred to in a Conclusion?

An effective Conclusion reiterates the issue or problem the hypothesis or objective(s) set out to solve. It is important to remind the readers what the hypothesis or objective(s) of the report are and to what extent they are addressed

How far should the Conclusion reflect the Introduction?

Referring to points made in the Introduction in the conclusion ties the paper together and provides readers with a sense of closure.

How much summarizing should there be in a Conclusion?

The conclusion can loosely follow the organization of your paper to parallel, but the focus should be on the paper’s analysis rather than on the organization.

Should newly found information be added to a Conclusion?

Well-written conclusions do not bring in new information or analysis; instead, they sum up what is already contained in the paper.

(Bahamani et al., 2017; Markowsky, 2010)

1.6 Task: Analysing a Conclusion Section

Consider Examples 1 to 4. How do the writers communicate the following information?

Restatement of objective(s)

Refection of outcome(s)

Acknowledgment of limitations, if any

Connection to wider context

“According to this study, the use of educational models, such as a Precaution Adoption Process Model (PAPM) that most people are associated with the process of decision-making in higher education will be beneficial. Moreover, in the preparation, development and implementation of training programs, factors like increased perceived susceptibility, and perceived benefits should be dealt with and some facilities should be provided to facilitate or resolve the barriers of doing the Pap smear test as much as possible.”

(Bahamani et al., 2016)

“Community pharmacists perceived the NMS service as being of benefit to patients by providing advice and reassurance. Implementation of NMS was variable and pharmacists’ perceptions of its feasibility and operationalisation were mixed. Some found the logistics of arranging and conducting the necessary follow-ups challenging, as were service targets. Patient awareness and understanding of NMS was reported to be low and there was a perceived need for publicity about the service. NMS appeared to have strengthened existing good relationships between pharmacists and GPs. Some pharmacists’ concerns about possible overlap of NMS with GP and nurse input may have impacted on their motivation. Overall, our findings indicate that NMS provides an opportunity for patient benefit (patient interaction and medicines management) and the development of contemporary pharmacy practice.”

(Lucas &amp; Blenkinsopp, 2015)

“In this review, we discussed several strategies for the engineering of RiPP pathways to produce artificial pep-tides bearing non-proteinogenic structures characteristic of peptidic natural products. In the RiPP pathways, the structures of the final products are defined by the primary sequences of the precursor genes. Moreover, only a small number of modifying enzymes are involved, and the enzymes function modularly. These features have greatly facilitated both in vivo and in vitro engineering of the pathways, leading to a wide variety of artificial derivatives of naturally occurring RiPPs. In principle, the engineering strategies introduced here can be interchangeably applied for other classes of RiPP enzymes/pathways. Post-biosynthetic chemical modification of RiPPs would be an alternative approach to further increase the structural variation of the products [48–50]. Given that new classes of RiPP enzymes have been frequently reported, and that genetic information of putative RiPP enzymes continues to arise, the array of molecules feasible by RiPP engineering will be further expanded. Some of the artificial RiPP derivatives exhibited elevated bioactivities or different selectivities as compared with their wild type RiPPs. Although these precedents have demonstrated the pharmaceutical relevance of RiPP ana-logs, the next important step in RiPP engineering is the development of novel RiPP derivatives with artificial bioactivities. In more recent reports [51 __,52 __,53 __], the integration of combinatorial lanthipeptide biosynthesis with in vitro selection or bacterial reverse two-hybrid screening methods have successfully obtained artificial ligands specific to certain target proteins. Such approaches, including other strategies under investigation in laboratories in this field, for constructing and screening vast RiPP libraries would lead to the creation of artificial bioactive peptides with non-proteinogenic structures in the near feature.”

(Goto &amp; Suga, 2018)

“Our study is the first to assess and characterise silibinin’s various roles as an adjuvant in protecting against PZA- and INH-induced hepatotoxicity. Most promisingly, we demonstrated silibinin’s safety and efficacy as a rescue adjuvant in vitro , both of which are fundamental considerations in the use of any drug. We also identified silibinin’s potential utility as a rescue hepatoprotectant, shed important mechanistic insights on its hepatoprotective effect, and identified novel antioxidant targets in ameliorating ATT-induced hepatotoxicity. The proof-of-concept demonstrated in this project forms the ethical and scientific foundation to justify and inform subsequent in vivo preclinical studies and clinical trials. Given the lack of alternative treatments in tuberculosis, the need to preserve our remaining antibiotics is paramount. The high stakes involved necessitate future efforts to support our preliminary work in making silibinin clinically relevant to patients and healthcare professionals alike.”

(Goh, 2018)

1.7 In Summary

To recap, in drafting the Conclusion section, you should keep in mind that final remarks can leave the readers with a long-lasting impression of the report especially on the key point(s) that the writer intends to convey. Therefore, you should be careful in crafting this last section of your report.

1.8 References

Bahamani, A. et al. (2017). The Effect of Training Based on Precaution Adoption Process Model (PAPM) on Rural Females’ Participation in Pap smear. BJPR, 16 , 6. Retrieved from http://www.journalrepository.org/media/journals/BJPR_14/2017/May/Bahmani1662017BJPR32965.pdf

Craswell G., &amp; Poore, M. (2012). Writing for Academic Success, 2nd. London: Sage.

Goh, Z-H. (2018). An Evaluation of the Roles and Mechanisms of Silibinin in Reducing Pyrazinamide- and Isoniazid-Induced Hepatotoxicity . Unpublished Final Year Project. National University of Singapore: Department of Pharmacy.

Goto, Y., &amp; Suga, H. (2018). Engineering of RiPP pathways for the production of artificial peptides bearing various non-proteinogenic structures. Current Opinion in Chemical Biology , 46 , 82–90.

Lucas, B., &amp; Blenkinsopp, A. (2015). Community pharmacists’ experience and perceptions of the New Medicines Serves (NMS). IJPP , 23 , 6. Retrieved from http://onlinelibrary.wiley.com/doi/10.1111/ijpp.12180/full

Markowski (2010). WPPD Evaluation form for capstone paper . Retrieved from https://cop-main.sites.medinfo.ufl.edu/files/2010/12/Capstone-Paper-Checklist-and-Reviewer-Evaluation-Form.pdf

Swales, J.M., &amp; Feak, C.B. (2012). Academic writing for graduate students , 3 rd ed. Michigan: University of Michigan Press.

University of North Carolina at Chapel Hill, The Writing Center. (2019). Conclusions . Retrieved from https://writingcenter.unc.edu/tips-and-tools/conclusions/

Appendix 2: Quiz for Conclusion Activity

Instructions

There are 6 questions in this quiz. Choose the most appropriate answer among the options provided.

What does the Conclusion section of a scientific report do?

It provides a recap of report, with reference to the objective(s).

It gives a closure to what has been discussed in relation to the topic.

It shares future direction(s) and in doing so connects to a wider context.

It propels the reader to have an enhanced understanding of the topic.

i, ii, and iii

i, ii and iv

ii, iii and iv

i, ii, iii and iv

The first rhetorical move of the Conclusion section is restatement of objective(s). It …

reminds the reader the objective(s) of the report.

restates reason(s) of each objective of the report.

revisits issue(s) presented requiring investigation.

reiterates the importance of the research project.

The second rhetorical move of the Conclusion section is reflection of outcome(s). It …

summarizes all the findings of the research project.

synthesizes outcomes of the research project.

is a repeat of important ideas mentioned in the report.

shows how key points, evidence, and support fit together.

In connecting to a wider context, the authors …

remind the reader of the importance of the topic.

propose a course of action for the reader.

pose a question to the reader for further research.

direct the reader to certain direction(s).

Following is the Conclusion section of a published article.

“In summary, we have assessed and characterised silibinin’s various roles as an adjuvant in protecting against PZA- and INH-induced hepatotoxicity. Our in vitro experiments suggest that silibinin may be safe and efficacious as a rescue adjuvant, both fundamental considerations in the use of any drug. Further optimisation of our in vitro model may also enhance silibinin’s hepatoprotective effect in rescue, prophylaxis, and recovery. Using this model, we have gleaned important mechanistic insights into its hepatoprotective effect and identified novel antioxidant targets in ameliorating HRZE-induced hepatotoxicity. Future directions will involve exploring the two main mechanisms by which silibinin may ameliorate hepatotoxicity; the proof-of-concept demonstrated in this project will inform subsequent in vitro and in vivo preclinical studies. Given the lack of alternative treatments in tuberculosis, the need to preserve our remaining antibiotics is paramount. These high stakes necessitate future efforts to support our preliminary work, making silibinin more clinically relevant to patients and healthcare professionals alike.” (Goh et al., 2020)

This excerpt of the Conclusion section…

restates objectives of the research.

synthesizes outcomes of the research.

acknowledges limitations of the research

connects the reader to a wider context.

i, ii and iii

What can one observe about the use of tenses in the Conclusion section? The frequency of use of present and future tenses …

demonstrates the importance results being synthesized.

is ungrammatical as the past tense should be used to state the outcomes.

propels the reader to think of future research.

suggests an encouraging tone to end the report.

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Wu, S.M., Lee, K.C., Chan, E.C.Y. (2023). The Conclusion: How to End a Scientific Report in Style. In: Rowland, S., Kuchel, L. (eds) Teaching Science Students to Communicate: A Practical Guide. Springer, Cham. https://doi.org/10.1007/978-3-030-91628-2_54

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How to Write a Conclusion for a Research Paper

• Posted on May 12, 2023

The key to an impactful research paper is crafting an effective conclusion. The conclusion provides a final opportunity to make a lasting impression on the reader by providing a powerful summary of the main argument and key findings.

A well-written conclusion not only summarizes your research but also ties everything back to your thesis statement. Plus, it provides important takeaways for your reader, highlighting what they should remember from your research and how it contributes to the larger academic discourse.

Crafting an impactful conclusion can be tricky, especially in argumentative papers. However, with our expert tips and tricks, you can rest assured that your conclusion will effectively restate the main argument and thesis statement in a way that resonates with your audience and elevates your research to new heights.

Why is a Conclusion Necessary for a Research Paper? 

The conclusion of a research paper is essential in tying together the different parts of the paper and offering a final perspective on the topic. It reinforces the main idea or argument presented and summarizes the key points and findings of the research, highlighting its significance. 

Additionally, the conclusion creates a full circle of the research by connecting back to the thesis statement presented at the paper’s beginning. It provides an opportunity to showcase the writer’s critical thinking skills by demonstrating how the research supports the main argument.

The conclusion is essential for a research paper because it provides closure for the reader. It serves as a final destination that helps the reader understand how all the different pieces of information fit together to support the main argument presented. It also offers insights into how the research can inform future studies and contribute to the larger academic discourse.

It also ensures that the reader does not get lost in the vast amount of information presented in the paper by providing a concise and coherent summary of the entire research. Additionally, it helps the reader identify the paper’s main takeaway and understand how the research contributes to the larger body of knowledge in the field.

Leave a Lasting Impression

A well-crafted conclusion is an essential element of any research paper. Its purpose is to leave a lasting impression on the reader and tie together the different parts of the paper.

To achieve this goal, a conclusion should summarize the main points and highlight the key findings of the research. By doing so, the reader can easily understand the focus and significance of the study.

A strong conclusion should also discuss any important findings that can be applied in the real world. This practical perspective gives readers a better sense of the impact and relevance of the research.

Summarize Your Thoughts

The conclusion of a research paper should be concise and provide a summary of the writer’s thoughts and ideas about the research. 

It should go beyond simply restating the main points and findings and address the “so what” of the research by explaining how it contributes to the existing body of knowledge on the same topic. This way, the conclusion can give readers a better understanding of the research’s significance and relevance to the broader academic community.

Demonstrate How Important Your Idea Is

Moving beyond a superficial overview and delving into the research in-depth is crucial to create a compelling conclusion. This entails summarizing the key findings of the study, highlighting its main contributions to the field, and placing the results in a broader context. Additionally, it would help if you comprehensively analyzed your work and its implications, underscoring its value to the broader academic community. 

New Insights

The conclusion section of a research paper offers an opportunity for the writer to present new insights and approaches to addressing the research problem.

Whether the research outcome is positive or negative, the conclusion provides a platform to discuss practical implications beyond the scope of the research paper. This discussion can help readers understand the potential impact of the research on the broader field and its significance for future research endeavors.

How to Write a Killer Conclusion with Key Points

When writing a conclusion for a research paper, it is important to cover several key points to create a solid and effective conclusion.

Restate the Thesis

When crafting a conclusion, restating the thesis statement is an important step that reminds readers of the research paper’s central focus. However, it should not be a verbatim repetition of the introduction. 

By restating the thesis concisely and clearly, you can effectively tie together the main ideas discussed in the body of the paper and emphasize the significance of the research question. However, keep in mind that the restated thesis should capture the essence of the paper and leave the reader with a clear understanding of the main topic and its importance.

Summarize the Main Points

To write an impactful conclusion, summarizing the main points discussed in the body of the paper is essential. This final section provides the writer with a last opportunity to highlight the significance of their research findings. 

However, it is equally important to avoid reiterating information already discussed in the body of the paper. Instead, you should synthesize and summarize the most significant points to emphasize the key findings. By doing so, the conclusion can effectively tie together the research findings and provide a clear understanding of the importance of the research topic.

Discuss the Results or Findings

The next step is to discuss the results or findings of the research. The discussion of the results or findings should not simply be a repetition of the information presented in the body of the paper.

Instead, it should provide a more in-depth analysis of the significance of the findings. This can involve explaining why the findings are important, what they mean in the context of the research question, and how they contribute to the field or area of study. 

Additionally, it’s crucial to address any limitations or weaknesses of the study in this section. This can provide a more balanced and nuanced understanding of the research and its implications. By doing so, the reader will have a better understanding of the scope and context of the study, which can ultimately enhance the credibility and validity of the research.

Ruminate on Your Thoughts

The final step to crafting an effective conclusion is to ruminate on your thoughts. This provides an opportunity to reflect on the meaning of the research and leaves the reader with something to ponder. Remember, the concluding paragraph should not introduce new information but rather summarize and reflect on the critical points made in the paper.

Furthermore, the conclusion should be integrated into the paper rather than presented as a separate section. It should provide a concise overview of the main findings and suggest avenues for further research.

Different Types of Conclusions 

There are various types of conclusions that can be employed to conclude a research paper effectively, depending on the research questions and topic being investigated.

Summarizing

Summarizing conclusions are frequently used to wrap up a research paper effectively. They restate the thesis statement and provide a brief overview of the main findings and outcomes of the research. This type of conclusion serves as a reminder to the reader of the key points discussed throughout the paper and emphasizes the significance of the research topic.

To be effective, summarizing conclusions should be concise and to the point, avoiding any new information not previously discussed in the body of the paper. Moreover, they are particularly useful when there is a clear and direct answer to the research question. This allows you to summarize your findings succinctly and leave the reader with a clear understanding of the implications of the research.

Externalizing

On the opposite end of the spectrum are externalizing conclusions. Unlike summarizing conclusions, externalizing conclusions introduce new ideas that may not be directly related to the research findings. This type of conclusion can be beneficial because it broadens the scope of the research topic and can lead to new insights and directions for future research.

By presenting new ideas, externalizing conclusions can challenge conventional thinking in the field and open up new avenues for exploration. This approach is instrumental in fields where research is ongoing, and new ideas and approaches are constantly being developed.

Editorial conclusions are a type of conclusion that allows the writer to express their commentary on the research findings. They can be particularly effective in connecting the writer’s insights with the research conducted and can offer a unique perspective on the research topic. Adding a personal touch to the conclusion can help engage the reader and leave a lasting impression.

Remember that regardless of the type of conclusion you choose, it should always start with a clear and concise restatement of the thesis statement, followed by a summary of the main findings in the body paragraphs. The first sentence of the conclusion should be impactful and attention-grabbing to make a strong impression on the reader.

What to Avoid in Your Conclusion

When crafting your conclusion, it’s essential to keep in mind several key points to ensure that it is effective and well-received by your audience:

• Avoid introducing new ideas or topics that have not been covered in the body of your paper.
• Refrain from simply restating what has already been said in your paper without adding new insights or analysis.
• Do not apologize for any shortcomings or limitations of your research, as this can undermine the importance of your findings.
• Avoid using overly emotional or flowery language, as it can detract from the professionalism and objectivity of the research.
• Lastly, avoid any examples of plagiarism. Be sure to properly cite any sources you have used in your research and writing.

Example of a Bad Conclusion

• Recapitulation without Insight: In conclusion, this paper has discussed the importance of exercise for physical and mental health. We hope this paper has been helpful to you and encourages you to start exercising today.
• Introduction of New Ideas: In conclusion, we have discussed the benefits of exercise and how it can improve physical and mental health. Additionally, we have highlighted the benefits of a plant-based diet and the importance of getting enough sleep for overall well-being.
• Emotional Language: In conclusion, exercise is good for your body and mind, and you should definitely start working out today!

Example of a Good Conclusion

• Insights and Implications: In light of our investigation, it is evident that regular exercise is undeniably beneficial for both physical and mental well-being, especially if performed at an appropriate duration and frequency. These findings hold significant implications for public health policies and personal wellness decisions.
• Limitations and Future Directions: While our investigation has shed light on the benefits of exercise, our study is not without limitations. Future research can delve deeper into the long-term effects of exercise on mental health and explore the impact of exercise on specific populations, such as older adults or individuals with chronic health conditions.
• Call to Action: In conclusion, we urge individuals to prioritize exercise as a critical component of their daily routine. By making exercise a habit, we can reap the many benefits of a healthy and active lifestyle.

Final Thoughts 

When writing a research paper, the conclusion is one of the most crucial elements to leave a lasting impression on the reader. It should effectively summarize the research and provide valuable insights, leaving the reader with something to ponder.

To accomplish this, it is essential to include vital elements, such as restating the thesis , summarizing the main points, and discussing the findings. However, it is equally important to avoid common mistakes that can undermine the effectiveness of the conclusion, such as introducing new information or repeating the introduction. 

So to ensure that your research is of the highest quality, it’s crucial to use proper citations and conduct a thorough literature review. Additionally, it is crucial to proofread the work to eliminate any errors. 

Fortunately, there are many available resources to help you with both writing and plagiarism prevention. Quetext , for example, offers a plagiarism checker, citation assistance, and proofreading tools to ensure the writing is top-notch. By incorporating these tips and using available resources, you can create a compelling and memorable conclusion for readers. 

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Writing a Paper: Conclusions

Writing a conclusion.

A conclusion is an important part of the paper; it provides closure for the reader while reminding the reader of the contents and importance of the paper. It accomplishes this by stepping back from the specifics in order to view the bigger picture of the document. In other words, it is reminding the reader of the main argument. For most course papers, it is usually one paragraph that simply and succinctly restates the main ideas and arguments, pulling everything together to help clarify the thesis of the paper. A conclusion does not introduce new ideas; instead, it should clarify the intent and importance of the paper. It can also suggest possible future research on the topic.

An Easy Checklist for Writing a Conclusion

It is important to remind the reader of the thesis of the paper so he is reminded of the argument and solutions you proposed.

Think of the main points as puzzle pieces, and the conclusion is where they all fit together to create a bigger picture. The reader should walk away with the bigger picture in mind.

Make sure that the paper places its findings in the context of real social change.

Make sure the reader has a distinct sense that the paper has come to an end. It is important to not leave the reader hanging. (You don’t want her to have flip-the-page syndrome, where the reader turns the page, expecting the paper to continue. The paper should naturally come to an end.)

No new ideas should be introduced in the conclusion. It is simply a review of the material that is already present in the paper. The only new idea would be the suggesting of a direction for future research.

Conclusion Example

As addressed in my analysis of recent research, the advantages of a later starting time for high school students significantly outweigh the disadvantages. A later starting time would allow teens more time to sleep--something that is important for their physical and mental health--and ultimately improve their academic performance and behavior. The added transportation costs that result from this change can be absorbed through energy savings. The beneficial effects on the students’ academic performance and behavior validate this decision, but its effect on student motivation is still unknown. I would encourage an in-depth look at the reactions of students to such a change. This sort of study would help determine the actual effects of a later start time on the time management and sleep habits of students.

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How to Write a Conclusion for a Research Paper

Find out which type of conclusion best suits your research, how to write it step-by-step, and common mistakes to avoid.

When writing a research paper, it can be challenging to make your point after providing an extensive amount of information. For this reason, a well-organized conclusion is essential. 

A research paper’s conclusion should be a brief summary of the paper’s substance and objectives; what you present in your research paper can gain impact by having a strong conclusion section.

In this Mind The Graph article, you will learn how to write a conclusion for a research report in a way that inspires action and helps the readers to better understand your research paper. This article will provide you the definition and some broad principles before providing step-by-step guidance.

What is a conclusion for a research paper and why is it important?

A conclusion is where you summarize the main points and, if appropriate, make new research suggestions. It is not merely a summary of the key points discussed or a rehash of your research question.

The reader is expected to comprehend from the article’s conclusion why your study should be significant to them after reading it. A conclusion of one or two well-developed paragraphs is appropriate for the majority of research papers; however, in a few unusual cases, more paragraphs may be required to highlight significant findings and their importance.

Just as the introduction is responsible for giving the reader a first impression on the subject, the conclusion is the chance to make a final impression by summarizing major information of your research paper and, most often, giving a different point of view on significant implications.

Adding a strong conclusion to your research paper is important because it’s a possibility to give the reader the comprehension of your research topic. Given that the reader is now fully informed on the subject, the conclusion also gives you a chance to restate the research problem effectively and concisely.

Examples of conclusions for a research paper

Now that you are aware of what a conclusion is and its significance for a research paper, it is time to provide you with some excellent samples of well-structured conclusions so you may get knowledge about the type of conclusion you can use for your research paper.

Argumentative Research Paper Conclusion

The most convincing arguments from your research paper should be added to the conclusion if you want to compose a strong argumentative conclusion.

Additionally, if your thesis statement expresses your perspective on the subject, you should think about restarting it as well as including any other pertinent information.

Example: As a result of the sixth extinction, which is currently affecting Earth, many species are vanishing every day. There are at least three strategies that people could employ to keep them from going extinct entirely in the ensuing fifty years. More recycling options, innovative plastic production techniques, and species preservation could save lives.

Analytical Research Paper Conclusion

The first thing you should do is reiterate your thesis and list the main elements of your arguments.

There should undoubtedly be a spotlight on a bigger context in the analytical research paper conclusion, which is the key distinction between it and other types of conclusions. It means you can add some meaning to the findings.

Example: Elon Musk has revolutionized the way we drive, pay for things, and even fly. His innovations are solely motivated by the desire to simplify things, but they inevitably alter the course of history. When Musk was a student, he had his first idea for PayPal, which is now among the most widely used methods of online payment. Likewise with Tesla automobiles.

Comparative Research Paper Conclusion

The conclusion of a comparative essay should be deeply analytical. To clearly express your conclusions, you must be very thorough when reviewing the data. Furthermore, the sources must be reliable.

A paraphrased thesis statement and a few sentences describing the significance of your study research are also required, as per normal.

Example: Gas-powered vehicles are ineffective and inefficient compared to electric vehicles. Not only do they emit fewer pollutants, but the drivers also get there more quickly. Additionally, gas cars cost more to maintain. Everything stems from the details of the far more straightforward engines used in electric cars.

How to write a conclusion for a research paper

In this section, you will learn how to write a conclusion for a research paper effectively and properly. These few easy steps will enable you to write the most convincing conclusion to your research paper.

1. Remember about the main topic

The statement must be written clearly and concisely to be effective, just one sentence. Remember that your conclusion should be concise and precise, expressing only the most important elements.

2. Reaffirm your thesis

Restate the research paper’s thesis after that. This can be done by going back to the original thesis that you presented in the research’s introduction. The thesis statement in your conclusion must be expressed differently from how it was in the introduction. This section can also be written effectively in a single sentence.

3. Sum important points in a summary

It’s time to make a list of the important arguments in your research paper. This phase can be made simpler by reading over your research and emphasizing only the main ideas and evidence.

Remember that the conclusion should not contain any new information. Focus only on the concepts you cover in your paper’s main body as a result. And also, keep in mind that this brief summary reminds your readers of the importance of the topic you are researching.

4. Emphasize the importance

At this stage, you can genuinely express a few words about how significant your arguments are. A succinct but impactful sentence can successfully achieve its aim. You could also attempt to examine this circumstance from a wider perspective.

Give an example of how your discoveries have affected a certain field. It would be beneficial if you made an effort to answer the question, “So what?” if there was any ambiguity.

5. Finish up your argument

As you wrap up your conclusion, consider posing a question or a call to action that will encourage readers to consider your point of view even further. This sentence can also answer any queries that were not addressed in the paper’s body paragraphs.

In addition, if there is an unresolved question in the main body, this is a fantastic area to comment on.

Common mistakes you should avoid

After learning the fundamentals of producing a strong research paper conclusion, it’s time to learn the common mistakes to avoid.

• Weak conclusion: If your ending is weak, readers will feel dissatisfied and disappointed. Writing ambiguous closing lines for essays also lowers the quality of the paper and the capacity of your arguments to support your main topic.
• Abrupt conclusion: Your research has to be an expression of your writing as a whole, not just a section. Therefore, make sure your thoughts are fully stated.
• Adding new information: Only your research should only be summarized in the conclusion. As the conclusion cannot contain extra information, make sure to offer all of your conclusions and supporting evidence in the body paragraphs.
• Absence of focus: A conclusion needs to be concise and well-focused. Avoid concluding the research with inane or superfluous details.
• Absurd length: Research must be of a proper length—neither too long nor too short. If you write more than is necessary, you can miss the point, which is to revisit the paper’s argument straightforwardly. Additionally, if you write too little, your readers will think you’re being negligent. It should be written in at least one or two whole paragraphs.

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How to Write a Conclusion for a Research Paper

Last Updated: May 8, 2024 Approved

This article was co-authored by Christopher Taylor, PhD . Christopher Taylor is an Adjunct Assistant Professor of English at Austin Community College in Texas. He received his PhD in English Literature and Medieval Studies from the University of Texas at Austin in 2014. wikiHow marks an article as reader-approved once it receives enough positive feedback. This article received 42 testimonials and 83% of readers who voted found it helpful, earning it our reader-approved status. This article has been viewed 2,259,696 times.

The conclusion of a research paper needs to summarize the content and purpose of the paper without seeming too wooden or dry. Every basic conclusion must share several key elements, but there are also several tactics you can play around with to craft a more effective conclusion and several you should avoid to prevent yourself from weakening your paper's conclusion. Here are some writing tips to keep in mind when creating a conclusion for your next research paper.

Sample Conclusions

Writing a basic conclusion.

• Do not spend a great amount of time or space restating your topic.
• A good research paper will make the importance of your topic apparent, so you do not need to write an elaborate defense of your topic in the conclusion.
• Usually a single sentence is all you need to restate your topic.
• An example would be if you were writing a paper on the epidemiology of infectious disease, you might say something like "Tuberculosis is a widespread infectious disease that affects millions of people worldwide every year."
• Yet another example from the humanities would be a paper about the Italian Renaissance: "The Italian Renaissance was an explosion of art and ideas centered around artists, writers, and thinkers in Florence."

• A thesis is a narrowed, focused view on the topic at hand.
• This statement should be rephrased from the thesis you included in your introduction. It should not be identical or too similar to the sentence you originally used.
• Try re-wording your thesis statement in a way that complements your summary of the topic of your paper in your first sentence of your conclusion.
• An example of a good thesis statement, going back to the paper on tuberculosis, would be "Tuberculosis is a widespread disease that affects millions of people worldwide every year. Due to the alarming rate of the spread of tuberculosis, particularly in poor countries, medical professionals are implementing new strategies for the diagnosis, treatment, and containment of this disease ."

• A good way to go about this is to re-read the topic sentence of each major paragraph or section in the body of your paper.
• Find a way to briefly restate each point mentioned in each topic sentence in your conclusion. Do not repeat any of the supporting details used within your body paragraphs.
• Under most circumstances, you should avoid writing new information in your conclusion. This is especially true if the information is vital to the argument or research presented in your paper.
• For example, in the TB paper you could summarize the information. "Tuberculosis is a widespread disease that affects millions of people worldwide. Due to the alarming rate of the spread of tuberculosis, particularly in poor countries, medical professionals are implementing new strategies for the diagnosis, treatment, and containment of this disease. In developing countries, such as those in Africa and Southeast Asia, the rate of TB infections is soaring. Crowded conditions, poor sanitation, and lack of access to medical care are all compounding factors in the spread of the disease. Medical experts, such as those from the World Health Organization are now starting campaigns to go into communities in developing countries and provide diagnostic testing and treatments. However, the treatments for TB are very harsh and have many side effects. This leads to patient non-compliance and spread of multi-drug resistant strains of the disease."

• Note that this is not needed for all research papers.
• If you already fully explained what the points in your paper mean or why they are significant, you do not need to go into them in much detail in your conclusion. Simply restating your thesis or the significance of your topic should suffice.
• It is always best practice to address important issues and fully explain your points in the body of your paper. The point of a conclusion to a research paper is to summarize your argument for the reader and, perhaps, to call the reader to action if needed.

• Note that a call for action is not essential to all conclusions. A research paper on literary criticism, for instance, is less likely to need a call for action than a paper on the effect that television has on toddlers and young children.
• A paper that is more likely to call readers to action is one that addresses a public or scientific need. Let's go back to our example of tuberculosis. This is a very serious disease that is spreading quickly and with antibiotic-resistant forms.
• A call to action in this research paper would be a follow-up statement that might be along the lines of "Despite new efforts to diagnose and contain the disease, more research is needed to develop new antibiotics that will treat the most resistant strains of tuberculosis and ease the side effects of current treatments."

• For example, if you are writing a history paper, then you might discuss how the historical topic you discussed matters today. If you are writing about a foreign country, then you might use the conclusion to discuss how the information you shared may help readers understand their own country.

Making Your Conclusion as Effective as Possible

• Since this sort of conclusion is so basic, you must aim to synthesize the information rather than merely summarizing it.
• Instead of merely repeating things you already said, rephrase your thesis and supporting points in a way that ties them all together.
• By doing so, you make your research paper seem like a "complete thought" rather than a collection of random and vaguely related ideas.

• Ask a question in your introduction. In your conclusion, restate the question and provide a direct answer.
• Write an anecdote or story in your introduction but do not share the ending. Instead, write the conclusion to the anecdote in the conclusion of your paper.
• For example, if you wanted to get more creative and put a more humanistic spin on a paper on tuberculosis, you might start your introduction with a story about a person with the disease, and refer to that story in your conclusion. For example, you could say something like this before you re-state your thesis in your conclusion: "Patient X was unable to complete the treatment for tuberculosis due to severe side effects and unfortunately succumbed to the disease."
• Use the same concepts and images introduced in your introduction in your conclusion. The images may or may not appear at other points throughout the research paper.

• Include enough information about your topic to back the statement up but do not get too carried away with excess detail.
• If your research did not provide you with a clear-cut answer to a question posed in your thesis, do not be afraid to indicate as much.
• Restate your initial hypothesis and indicate whether you still believe it or if the research you performed has begun swaying your opinion.
• Indicate that an answer may still exist and that further research could shed more light on the topic at hand.

• This may not be appropriate for all types of research papers. Most research papers, such as one on effective treatment for diseases, will have the information to make the case for a particular argument already in the paper.
• A good example of a paper that might ask a question of the reader in the ending is one about a social issue, such as poverty or government policy.
• Ask a question that will directly get at the heart or purpose of the paper. This question is often the same question, or some version of it, that you may have started with when you began your research.
• Make sure that the question can be answered by the evidence presented in your paper.
• If desired you can briefly summarize the answer after stating the question. You could also leave the question hanging for the reader to answer, though.

• Even without a call to action, you can still make a recommendation to your reader.
• For instance, if you are writing about a topic like third-world poverty, you can various ways for the reader to assist in the problem without necessarily calling for more research.
• Another example would be, in a paper about treatment for drug-resistant tuberculosis, you could suggest donating to the World Health Organization or research foundations that are developing new treatments for the disease.

Avoiding Common Pitfalls

• These sayings usually sound stiff, unnatural, or trite when used in writing.
• Moreover, using a phrase like "in conclusion" to begin your conclusion is a little too straightforward and tends to lead to a weak conclusion. A strong conclusion can stand on its own without being labeled as such.

• Always state the main argument or thesis in the introduction. A research paper is an analytical discussion of an academic topic, not a mystery novel.
• A good, effective research paper will allow your reader to follow your main argument from start to finish.
• This is why it is best practice to start your paper with an introduction that states your main argument and to end the paper with a conclusion that re-states your thesis for re-iteration.

• All significant information should be introduced in the body of the paper.
• Supporting evidence expands the topic of your paper by making it appear more detailed. A conclusion should narrow the topic to a more general point.
• A conclusion should only summarize what you have already stated in the body of your paper.
• You may suggest further research or a call to action, but you should not bring in any new evidence or facts in the conclusion.

• Most often, a shift in tone occurs when a research paper with an academic tone gives an emotional or sentimental conclusion.
• Even if the topic of the paper is of personal significance for you, you should not indicate as much in your paper.
• If you want to give your paper a more humanistic slant, you could start and end your paper with a story or anecdote that would give your topic more personal meaning to the reader.
• This tone should be consistent throughout the paper, however.

• Apologetic statements include phrases like "I may not be an expert" or "This is only my opinion."
• Statements like this can usually be avoided by refraining from writing in the first-person.
• Avoid any statements in the first-person. First-person is generally considered to be informal and does not fit with the formal tone of a research paper.

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• ↑ http://owl.english.purdue.edu/owl/resource/724/04/
• ↑ http://www.crlsresearchguide.org/18_Writing_Conclusion.asp
• ↑ http://writing.wisc.edu/Handbook/PlanResearchPaper.html#conclusion
• ↑ http://writingcenter.unc.edu/handouts/conclusions/
• ↑ http://writing2.richmond.edu/writing/wweb/conclude.html

About This Article

To write a conclusion for a research paper, start by restating your thesis statement to remind your readers what your main topic is and bring everything full circle. Then, briefly summarize all of the main points you made throughout your paper, which will help remind your readers of everything they learned. You might also want to include a call to action if you think more research or work needs to be done on your topic by writing something like, "Despite efforts to contain the disease, more research is needed to develop antibiotics." Finally, end your conclusion by explaining the broader context of your topic and why your readers should care about it, which will help them understand why your topic is relevant and important. For tips from our Academic co-author, like how to avoid common pitfalls when writing your conclusion, scroll down! Did this summary help you? Yes No

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How to Write a Research Paper Conclusion Section

What is a conclusion in a research paper?

The conclusion in a research paper is the final paragraph or two in a research paper. In scientific papers, the conclusion usually follows the Discussion section , summarizing the importance of the findings and reminding the reader why the work presented in the paper is relevant.

However, it can be a bit confusing to distinguish the conclusion section/paragraph from a summary or a repetition of your findings, your own opinion, or the statement of the implications of your work. In fact, the conclusion should contain a bit of all of these other parts but go beyond it—but not too far beyond! 

The structure and content of the conclusion section can also vary depending on whether you are writing a research manuscript or an essay. This article will explain how to write a good conclusion section, what exactly it should (and should not) contain, how it should be structured, and what you should avoid when writing it.  

Table of Contents:

What does a good conclusion section do, what to include in a research paper conclusion.

• Conclusion in an Essay
• Research Paper Conclusion 
• Conclusion Paragraph Outline and Example
• What Not to Do When Writing a Conclusion

The conclusion of a research paper has several key objectives. It should:

• Restate your research problem addressed in the introduction section
• Summarize your main arguments, important findings, and broader implications
• Synthesize key takeaways from your study

The specific content in the conclusion depends on whether your paper presents the results of original scientific research or constructs an argument through engagement with previously published sources.

You presented your general field of study to the reader in the introduction section, by moving from general information (the background of your work, often combined with a literature review ) to the rationale of your study and then to the specific problem or topic you addressed, formulated in the form of the statement of the problem in research or the thesis statement in an essay.

In the conclusion section, in contrast, your task is to move from your specific findings or arguments back to a more general depiction of how your research contributes to the readers’ understanding of a certain concept or helps solve a practical problem, or fills an important gap in the literature. The content of your conclusion section depends on the type of research you are doing and what type of paper you are writing. But whatever the outcome of your work is, the conclusion is where you briefly summarize it and place it within a larger context. It could be called the “take-home message” of the entire paper.

What to summarize in the conclusion

Your conclusion section needs to contain a very brief summary of your work , a very brief summary of the main findings of your work, and a mention of anything else that seems relevant when you now look at your work from a bigger perspective, even if it was not initially listed as one of your main research questions. This could be a limitation, for example, a problem with the design of your experiment that either needs to be considered when drawing any conclusions or that led you to ask a different question and therefore draw different conclusions at the end of your study (compared to when you started out).

Once you have reminded the reader of what you did and what you found, you need to go beyond that and also provide either your own opinion on why your work is relevant (and for whom, and how) or theoretical or practical implications of the study , or make a specific call for action if there is one to be made.   

How to Write an Essay Conclusion

Academic essays follow quite different structures than their counterparts in STEM and the natural sciences. Humanities papers often have conclusion sections that are much longer and contain more detail than scientific papers. There are three main types of academic essay conclusions.

Summarizing conclusion

The most typical conclusion at the end of an analytical/explanatory/argumentative essay is a summarizing conclusion . This is, as the name suggests, a clear summary of the main points of your topic and thesis. Since you might have gone through a number of different arguments or subtopics in the main part of your essay, you need to remind the reader again what those were, how they fit into each other, and how they helped you develop or corroborate your hypothesis.

For an essay that analyzes how recruiters can hire the best candidates in the shortest time or on “how starving yourself will increase your lifespan, according to science”, a summary of all the points you discussed might be all you need. Note that you should not exactly repeat what you said earlier, but rather highlight the essential details and present those to your reader in a different way. 

Externalizing conclusion

If you think that just reminding the reader of your main points is not enough, you can opt for an externalizing conclusion instead, that presents new points that were not presented in the paper so far. These new points can be additional facts and information or they can be ideas that are relevant to the topic and have not been mentioned before.

Such a conclusion can stimulate your readers to think about your topic or the implications of your analysis in a whole new way. For example, at the end of a historical analysis of a specific event or development, you could direct your reader’s attention to some current events that were not the topic of your essay but that provide a different context for your findings.

Editorial conclusion

In an editorial conclusion , another common type of conclusion that you will find at the end of papers and essays, you do not add new information but instead present your own experiences or opinions on the topic to round everything up. What makes this type of conclusion interesting is that you can choose to agree or disagree with the information you presented in your paper so far. For example, if you have collected and analyzed information on how a specific diet helps people lose weight, you can nevertheless have your doubts on the sustainability of that diet or its practicability in real life—if such arguments were not included in your original thesis and have therefore not been covered in the main part of your paper, the conclusion section is the place where you can get your opinion across.    

How to Conclude an Empirical Research Paper

An empirical research paper is usually more concise and succinct than an essay, because, if it is written well, it focuses on one specific question, describes the method that was used to answer that one question, describes and explains the results, and guides the reader in a logical way from the introduction to the discussion without going on tangents or digging into not absolutely relevant topics.

Summarize the findings

In a scientific paper, you should include a summary of the findings. Don’t go into great detail here (you will have presented your in-depth  results  and  discussion  already), but do clearly express the answers to the  research questions  you investigated.

Describe your main findings, even if they weren’t necessarily the ones anticipated, and explain the conclusion they led you to. Explain these findings in as few words as possible.

Instead of beginning with “ In conclusion, in this study, we investigated the effect of stress on the brain using fMRI …”, you should try to find a way to incorporate the repetition of the essential (and only the essential) details into the summary of the key points. “ The findings of this fMRI study on the effect of stress on the brain suggest that …” or “ While it has been known for a long time that stress has an effect on the brain, the findings of this fMRI study show that, surprisingly… ” would be better ways to start a conclusion. 

You should also not bring up new ideas or present new facts in the conclusion of a research paper, but stick to the background information you have presented earlier, to the findings you have already discussed, and the limitations and implications you have already described. The one thing you can add here is a practical recommendation that you haven’t clearly stated before—but even that one needs to follow logically from everything you have already discussed in the discussion section.

Discuss the implications

After summing up your key arguments or findings, conclude the paper by stating the broader implications of the research , whether in methods , approach, or findings. Express practical or theoretical takeaways from your paper. This often looks like a “call to action” or a final “sales pitch” that puts an exclamation point on your paper.

If your research topic is more theoretical in nature, your closing statement should express the significance of your argument—for example, in proposing a new understanding of a topic or laying the groundwork for future research.

Future research example

Future research into education standards should focus on establishing a more detailed picture of how novel pedagogical approaches impact young people’s ability to absorb new and difficult concepts. Moreover, observational studies are needed to gain more insight into how specific teaching models affect the retention of relationships and facts—for instance, how inquiry-based learning and its emphasis on lateral thinking can be used as a jumping-off point for more holistic classroom approaches.

Research Conclusion Example and Outline

Let’s revisit the study on the effect of stress on the brain we mentioned before and see what the common structure for a conclusion paragraph looks like, in three steps. Following these simple steps will make it easy for you to wrap everything up in one short paragraph that contains all the essential information: 

One: Short summary of what you did, but integrated into the summary of your findings:

While it has been known for a long time that stress has an effect on the brain, the findings of this fMRI study in 25 university students going through mid-term exams show that, surprisingly, one’s attitude to the experienced stress significantly modulates the brain’s response to it. 

Note that you don’t need to repeat any methodological or technical details here—the reader has been presented with all of these before, they have read your results section and the discussion of your results, and even (hopefully!) a discussion of the limitations and strengths of your paper. The only thing you need to remind them of here is the essential outcome of your work. 

Two: Add implications, and don’t forget to specify who this might be relevant for: 

Students could be considered a specific subsample of the general population, but earlier research shows that the effect that exam stress has on their physical and mental health is comparable to the effects of other types of stress on individuals of other ages and occupations. Further research into practical ways of modulating not only one’s mental stress response but potentially also one’s brain activity (e.g., via neurofeedback training) are warranted.

This is a “research implication”, and it is nicely combined with a mention of a potential limitation of the study (the student sample) that turns out not to be a limitation after all (because earlier research suggests we can generalize to other populations). If there already is a lot of research on neurofeedback for stress control, by the way, then this should have been discussed in your discussion section earlier and you wouldn’t say such studies are “warranted” here but rather specify how your findings could inspire specific future experiments or how they should be implemented in existing applications. 

Three: The most important thing is that your conclusion paragraph accurately reflects the content of your paper. Compare it to your research paper title , your research paper abstract , and to your journal submission cover letter , in case you already have one—if these do not all tell the same story, then you need to go back to your paper, start again from the introduction section, and find out where you lost the logical thread. As always, consistency is key.    

Problems to Avoid When Writing a Conclusion 

• Do not suddenly introduce new information that has never been mentioned before (unless you are writing an essay and opting for an externalizing conclusion, see above). The conclusion section is not where you want to surprise your readers, but the take-home message of what you have already presented.
• Do not simply copy your abstract, the conclusion section of your abstract, or the first sentence of your introduction, and put it at the end of the discussion section. Even if these parts of your paper cover the same points, they should not be identical.
• Do not start the conclusion with “In conclusion”. If it has its own section heading, that is redundant, and if it is the last paragraph of the discussion section, it is inelegant and also not really necessary. The reader expects you to wrap your work up in the last paragraph, so you don’t have to announce that. Just look at the above example to see how to start a conclusion in a natural way.
• Do not forget what your research objectives were and how you initially formulated the statement of the problem in your introduction section. If your story/approach/conclusions changed because of methodological issues or information you were not aware of when you started, then make sure you go back to the beginning and adapt your entire story (not just the ending). 

Consider Receiving Academic Editing Services

When you have arrived at the conclusion of your paper, you might want to head over to Wordvice AI’s AI Writing Assistant to receive a free grammar check for any academic content. 

After drafting, you can also receive English editing and proofreading services , including paper editing services for your journal manuscript. If you need advice on how to write the other parts of your research paper , or on how to make a research paper outline if you are struggling with putting everything you did together, then head over to the Wordvice academic resources pages , where we have a lot more articles and videos for you.

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Evans D, Coad J, Cottrell K, et al. Public involvement in research: assessing impact through a realist evaluation. Southampton (UK): NIHR Journals Library; 2014 Oct. (Health Services and Delivery Research, No. 2.36.)

Public involvement in research: assessing impact through a realist evaluation.

Chapter 9 conclusions and recommendations for future research.

• How well have we achieved our original aim and objectives?

The initially stated overarching aim of this research was to identify the contextual factors and mechanisms that are regularly associated with effective and cost-effective public involvement in research. While recognising the limitations of our analysis, we believe we have largely achieved this in our revised theory of public involvement in research set out in Chapter 8 . We have developed and tested this theory of public involvement in research in eight diverse case studies; this has highlighted important contextual factors, in particular PI leadership, which had not previously been prominent in the literature. We have identified how this critical contextual factor shapes key mechanisms of public involvement, including the identification of a senior lead for involvement, resource allocation for involvement and facilitation of research partners. These mechanisms then lead to specific outcomes in improving the quality of research, notably recruitment strategies and materials and data collection tools and methods. We have identified a ‘virtuous circle’ of feedback to research partners on their contribution leading to their improved confidence and motivation, which facilitates their continued contribution. Following feedback from the HS&DR Board on our original application we did not seek to assess the cost-effectiveness of different mechanisms of public involvement but we did cost the different types of public involvement as discussed in Chapter 7 . A key finding is that many research projects undercost public involvement.

In our original proposal we emphasised our desire to include case studies involving young people and families with children in the research process. We recruited two studies involving parents of young children aged under 5 years, and two projects involving ‘older’ young people in the 18- to 25-years age group. We recognise that in doing this we missed studies involving children and young people aged under 18 years; in principle we would have liked to have included studies involving such children and young people, but, given the resources at our disposal and the additional resource, ethical and governance issues this would have entailed, we regretfully concluded that this would not be feasible for our study. In terms of the four studies with parental and young persons’ involvement that we did include, we have not done a separate analysis of their data, but the themes emerging from those case studies were consistent with our other case studies and contributed to our overall analysis.

In terms of the initial objectives, we successfully recruited the sample of eight diverse case studies and collected and analysed data from them (objective 1). As intended, we identified the outcomes of involvement from multiple stakeholders‘ perspectives, although we did not get as many research partners‘ perspectives as we would have liked – see limitations below (objective 2). It was more difficult than expected to track the impact of public involvement from project inception through to completion (objective 3), as all of our projects turned out to have longer time scales than our own. Even to track involvement over a stage of a case study research project proved difficult, as the research usually did not fall into neatly staged time periods and one study had no involvement activity over the study period.

Nevertheless, we were able to track seven of the eight case studies prospectively and in real time over time periods of up to 9 months, giving us an unusual window on involvement processes that have previously mainly been observed retrospectively. We were successful in comparing the contextual factors, mechanisms and outcomes associated with public involvement from different stakeholders‘ perspectives and costing the different mechanisms for public involvement (objective 4). We only partly achieved our final objective of undertaking a consensus exercise among stakeholders to assess the merits of the realist evaluation approach and our approach to the measurement and valuation of economic costs of public involvement in research (objective 5). A final consensus event was held, where very useful discussion and amendment of our theory of public involvement took place, and the economic approach was discussed and helpfully critiqued by participants. However, as our earlier discussions developed more fully than expected, we decided to let them continue rather than interrupt them in order to run the final exercise to assess the merits of the realist evaluation approach. We did, however, test our analysis with all our case study participants by sending a draft of this final report for comment. We received a number of helpful comments and corrections but no disagreement with our overall analysis.

• What were the limitations of our study?

Realist evaluation is a relatively new approach and we recognise that there were a number of limitations to our study. We sought to follow the approach recommended by Pawson, but we acknowledge that we were not always able to do so. In particular, our theory of public involvement in research evolved over time and initially was not as tightly framed in terms of a testable hypothesis as Pawson recommends. In his latest book Pawson strongly recommends that outcomes should be measured with quantitative data, 17 but we did not do so; we were not aware of the existence of quantitative data or tools that would enable us to collect such data to answer our research questions. Even in terms of qualitative data, we did not capture as much information on outcomes as we initially envisaged. There were several reasons for this. The most important was that capturing outcomes in public involvement is easier the more operational the focus of involvement, and more difficult the more strategic the involvement. Thus, it was relatively easy to see the impact of a patient panel on the redesign of a recruitment leaflet but harder to capture the impact of research partners in a multidisciplinary team discussion of research design.

We also found it was sometimes more difficult to engage research partners as participants in our research than researchers or research managers. On reflection this is not surprising. Research partners are generally motivated to take part in research relevant to their lived experience of a health condition or situation, whereas our research was quite detached from their lived experience; in addition people had many constraints on their time, so getting involved in our research as well as their own was likely to be a burden too far for some. Researchers clearly also face significant time pressures but they had a more direct interest in our research, as they are obliged to engage with public involvement to satisfy research funders such as the NIHR. Moreover, researchers were being paid by their employers for their time during interviews with us, while research partners were not paid by us and usually not paid by their research teams. Whatever the reasons, we had less response from research partners than researchers or research managers, particularly for the third round of data collection; thus we have fewer data on outcomes from research partners‘ perspectives and we need to be aware of a possible selection bias towards more engaged research partners. Such a bias could have implications for our findings; for example payment might have been a more important motivating factor for less engaged advisory group members.

There were a number of practical difficulties we encountered. One challenge was when to recruit the case studies. We recruited four of our eight case studies prior to the full application, but this was more than 1 year before our project started and 15 months or more before data collection began. In this intervening period, we found that the time scales of some of the case studies were no longer ideal for our project and we faced the choice of whether to continue with them, although this timing was not ideal, or seek at a late moment to recruit alternative ones. One of our case studies ultimately undertook no involvement activity over the study period, so we obtained fewer data from it, and it contributed relatively little to our analysis. Similarly, one of the four case studies we recruited later experienced some delays itself in beginning and so we had a more limited period for data collection than initially envisaged. Research governance approvals took much longer than expected, particularly as we had to take three of our research partners, who were going to collect data within NHS projects, through the research passport process, which essentially truncated our data collection period from 1 year to 9 months. Even if we had had the full year initially envisaged for data collection, our conclusion with hindsight was that this was insufficiently long. To compare initial plans and intentions for involvement with the reality of what actually happened required a longer time period than a year for most of our case studies.

In the light of the importance we have placed on the commitment of PIs, there is an issue of potential selection bias in the recruitment of our sample. As our sampling strategy explicitly involved a networking approach to PIs of projects where we thought some significant public involvement was taking place, we were likely (as we did) to recruit enthusiasts and, at worst, those non-committed who were at least open to the potential value of public involvement. There were, unsurprisingly, no highly sceptical PIs in our sample. We have no data therefore on how public involvement may work in research where the PI is sceptical but may feel compelled to undertake involvement because of funder requirements or other factors.

• What would we do differently next time?

If we were to design this study again, there are a number of changes we would make. Most importantly we would go for a longer time period to be able to capture involvement through the whole research process from initial design through to dissemination. We would seek to recruit far more potential case studies in principle, so that we had greater choice of which to proceed with once our study began in earnest. We would include case studies from the application stage to capture the important early involvement of research partners in the initial design period. It might be preferable to research a smaller number of case studies, allowing a more in-depth ethnographic approach. Although challenging, it would be very informative to seek to sample sceptical PIs. This might require a brief screening exercise of a larger group of PIs on their attitudes to and experience of public involvement.

The economic evaluation was challenging in a number of ways, particularly in seeking to obtain completed resource logs from case study research partners. Having a 2-week data collection period was also problematic in a field such as public involvement, where activity may be very episodic and infrequent. Thus, collecting economic data alongside other case study data in a more integrated way, and particularly with interviews and more ethnographic observation of case study activities, might be advantageous. The new budgeting tool developed by INVOLVE and the MHRN may provide a useful resource for future economic evaluations. 23

We have learned much from the involvement of research partners in our research team and, although many aspects of our approach worked well, there are some things we would do differently in future. Even though we included substantial resources for research partner involvement in all aspects of our study, we underestimated how time-consuming such full involvement would be. We were perhaps overambitious in trying to ensure such full involvement with the number of research partners and the number and complexity of the case studies. We were also perhaps naive in expecting all the research partners to play the same role in the team; different research partners came with different experiences and skills, and, like most of our case studies, we might have been better to be less prescriptive and allow the roles to develop more organically within the project.

• Implications for research practice and funding

If one of the objectives of R&D policy is to increase the extent and effectiveness of public involvement in research, then a key implication of this research is the importance of influencing PIs to value public involvement in research or to delegate to other senior colleagues in leading on involvement in their research. Training is unlikely to be the key mechanism here; senior researchers are much more likely to be influenced by peers or by their personal experience of the benefits of public involvement. Early career researchers may be shaped by training but again peer learning and culture may be more influential. For those researchers sceptical or agnostic about public involvement, the requirement of funders is a key factor that is likely to make them engage with the involvement agenda. Therefore, funders need to scrutinise the track record of research teams on public involvement to ascertain whether there is any evidence of commitment or leadership on involvement.

One of the findings of the economic analysis was that PIs have consistently underestimated the costs of public involvement in their grant applications. Clearly the field will benefit from the guidance and budgeting tool recently disseminated by MHRN and INVOLVE. It was also notable that there was a degree of variation in the real costs of public involvement and that effective involvement is not necessarily costly. Different models of involvement incur different costs and researchers need to be made aware of the costs and benefits of these different options.

One methodological lesson we learned was the impact that conducting this research had on some participants’ reflection on the impact of public involvement. Particularly for research staff, the questions we asked sometimes made them reflect upon what they were doing and change aspects of their approach to involvement. Thus, the more the NIHR and other funders can build reporting, audit and other forms of evaluation on the impact of public involvement directly into their processes with PIs, the more likely such questioning might stimulate similar reflection.

• Recommendations for further research

There are a number of gaps in our knowledge around public involvement in research that follow from our findings, and would benefit from further research, including realist evaluation to extend and further test the theory we have developed here:

• In-depth exploration of how PIs become committed to public involvement and how to influence agnostic or sceptical PIs would be very helpful. Further research might compare, for example, training with peer-influencing strategies in engendering PI commitment. Research could explore the leadership role of other research team members, including research partners, and how collective leadership might support effective public involvement.
• More methodological work is needed on how to robustly capture the impact and outcomes of public involvement in research (building as well on the PiiAF work of Popay et al. 51 ), including further economic analysis and exploration of impact when research partners are integral to research teams.
• Research to develop approaches and carry out a full cost–benefit analysis of public involvement in research would be beneficial. Although methodologically challenging, it would be very useful to conduct some longer-term studies which sought to quantify the impact of public involvement on such key indicators as participant recruitment and retention in clinical trials.
• It would also be helpful to capture qualitatively the experiences and perspectives of research partners who have had mixed or negative experiences, since they may be less likely than enthusiasts to volunteer to participate in studies of involvement in research such as ours. Similarly, further research might explore the (relatively rare) experiences of marginalised and seldom-heard groups involved in research.
• Payment for public involvement in research remains a contested issue with strongly held positions for and against; it would be helpful to further explore the value research partners and researchers place on payment and its effectiveness for enhancing involvement in and impact on research.
• A final relatively narrow but important question that we identified after data collection had finished is: what is the impact of the long periods of relative non-involvement following initial periods of more intense involvement for research partners in some types of research, particularly clinical trials?

Included under terms of UK Non-commercial Government License .

• Cite this Page Evans D, Coad J, Cottrell K, et al. Public involvement in research: assessing impact through a realist evaluation. Southampton (UK): NIHR Journals Library; 2014 Oct. (Health Services and Delivery Research, No. 2.36.) Chapter 9, Conclusions and recommendations for future research.
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What I’ve Learned From My Students’ College Essays

The genre is often maligned for being formulaic and melodramatic, but it’s more important than you think.

By Nell Freudenberger

Most high school seniors approach the college essay with dread. Either their upbringing hasn’t supplied them with several hundred words of adversity, or worse, they’re afraid that packaging the genuine trauma they’ve experienced is the only way to secure their future. The college counselor at the Brooklyn high school where I’m a writing tutor advises against trauma porn. “Keep it brief , ” she says, “and show how you rose above it.”

I started volunteering in New York City schools in my 20s, before I had kids of my own. At the time, I liked hanging out with teenagers, whom I sometimes had more interesting conversations with than I did my peers. Often I worked with students who spoke English as a second language or who used slang in their writing, and at first I was hung up on grammar. Should I correct any deviation from “standard English” to appeal to some Wizard of Oz behind the curtains of a college admissions office? Or should I encourage students to write the way they speak, in pursuit of an authentic voice, that most elusive of literary qualities?

In fact, I was missing the point. One of many lessons the students have taught me is to let the story dictate the voice of the essay. A few years ago, I worked with a boy who claimed to have nothing to write about. His life had been ordinary, he said; nothing had happened to him. I asked if he wanted to try writing about a family member, his favorite school subject, a summer job? He glanced at his phone, his posture and expression suggesting that he’d rather be anywhere but in front of a computer with me. “Hobbies?” I suggested, without much hope. He gave me a shy glance. “I like to box,” he said.

I’ve had this experience with reluctant writers again and again — when a topic clicks with a student, an essay can unfurl spontaneously. Of course the primary goal of a college essay is to help its author get an education that leads to a career. Changes in testing policies and financial aid have made applying to college more confusing than ever, but essays have remained basically the same. I would argue that they’re much more than an onerous task or rote exercise, and that unlike standardized tests they are infinitely variable and sometimes beautiful. College essays also provide an opportunity to learn precision, clarity and the process of working toward the truth through multiple revisions.

When a topic clicks with a student, an essay can unfurl spontaneously.

Even if writing doesn’t end up being fundamental to their future professions, students learn to choose language carefully and to be suspicious of the first words that come to mind. Especially now, as college students shoulder so much of the country’s ethical responsibility for war with their protest movement, essay writing teaches prospective students an increasingly urgent lesson: that choosing their own words over ready-made phrases is the only reliable way to ensure they’re thinking for themselves.

Teenagers are ideal writers for several reasons. They’re usually free of preconceptions about writing, and they tend not to use self-consciously ‘‘literary’’ language. They’re allergic to hypocrisy and are generally unfiltered: They overshare, ask personal questions and call you out for microaggressions as well as less egregious (but still mortifying) verbal errors, such as referring to weed as ‘‘pot.’’ Most important, they have yet to put down their best stories in a finished form.

I can imagine an essay taking a risk and distinguishing itself formally — a poem or a one-act play — but most kids use a more straightforward model: a hook followed by a narrative built around “small moments” that lead to a concluding lesson or aspiration for the future. I never get tired of working with students on these essays because each one is different, and the short, rigid form sometimes makes an emotional story even more powerful. Before I read Javier Zamora’s wrenching “Solito,” I worked with a student who had been transported by a coyote into the U.S. and was reunited with his mother in the parking lot of a big-box store. I don’t remember whether this essay focused on specific skills or coping mechanisms that he gained from his ordeal. I remember only the bliss of the parent-and-child reunion in that uninspiring setting. If I were making a case to an admissions officer, I would suggest that simply being able to convey that experience demonstrates the kind of resilience that any college should admire.

The essays that have stayed with me over the years don’t follow a pattern. There are some narratives on very predictable topics — living up to the expectations of immigrant parents, or suffering from depression in 2020 — that are moving because of the attention with which the student describes the experience. One girl determined to become an engineer while watching her father build furniture from scraps after work; a boy, grieving for his mother during lockdown, began taking pictures of the sky.

If, as Lorrie Moore said, “a short story is a love affair; a novel is a marriage,” what is a college essay? Every once in a while I sit down next to a student and start reading, and I have to suppress my excitement, because there on the Google Doc in front of me is a real writer’s voice. One of the first students I ever worked with wrote about falling in love with another girl in dance class, the absolute magic of watching her move and the terror in the conflict between her feelings and the instruction of her religious middle school. She made me think that college essays are less like love than limerence: one-sided, obsessive, idiosyncratic but profound, the first draft of the most personal story their writers will ever tell.

Nell Freudenberger’s novel “The Limits” was published by Knopf last month. She volunteers through the PEN America Writers in the Schools program.

• Open access
• Published: 13 May 2024

Aerobic anoxygenic phototrophs play important roles in nutrient cycling within cyanobacterial Microcystis bloom microbiomes

• Haiyuan Cai 1 , 2 ,
• Christopher J. McLimans 1 ,
• Helong Jiang 2 ,
• Feng Chen 3 ,
• Lee R. Krumholz 1 &
• K. David Hambright 1  

Microbiome volume  12 , Article number:  88 ( 2024 ) Cite this article

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During the bloom season, the colonial cyanobacterium Microcystis forms complex aggregates which include a diverse microbiome within an exopolymer matrix. Early research postulated a simple mutualism existing with bacteria benefitting from the rich source of fixed carbon and Microcystis receiving recycled nutrients. Researchers have since hypothesized that Microcystis aggregates represent a community of synergistic and interacting species, an interactome, each with unique metabolic capabilities that are critical to the growth, maintenance, and demise of Microcystis blooms. Research has also shown that aggregate-associated bacteria are taxonomically different from free-living bacteria in the surrounding water. Moreover, research has identified little overlap in functional potential between Microcystis and members of its microbiome, further supporting the interactome concept. However, we still lack verification of general interaction and know little about the taxa and metabolic pathways supporting nutrient and metabolite cycling within Microcystis aggregates.

During a 7-month study of bacterial communities comparing free-living and aggregate-associated bacteria in Lake Taihu, China, we found that aerobic anoxygenic phototrophic (AAP) bacteria were significantly more abundant within Microcystis aggregates than in free-living samples, suggesting a possible functional role for AAP bacteria in overall aggregate community function. We then analyzed gene composition in 102 high-quality metagenome-assembled genomes (MAGs) of bloom-microbiome bacteria from 10 lakes spanning four continents, compared with 12 complete Microcystis genomes which revealed that microbiome bacteria and Microcystis possessed complementary biochemical pathways that could serve in C, N, S, and P cycling. Mapping published transcripts from Microcystis blooms onto a comprehensive AAP and non-AAP bacteria MAG database (226 MAGs) indicated that observed high levels of expression of genes involved in nutrient cycling pathways were in AAP bacteria.

Conclusions

Our results provide strong corroboration of the hypothesized Microcystis interactome and the first evidence that AAP bacteria may play an important role in nutrient cycling within Microcystis aggregate microbiomes.

Video Abstract

Introduction

Harmful algal blooms caused by cyanobacteria in freshwater lakes are a global ecological problem [ 1 , 2 ]. Eutrophication, rising CO 2 levels, and global warming are likely to increase cyanobacterial bloom frequency, intensity, and duration in aquatic ecosystems across the globe [ 3 , 4 ]. Microcystis spp. are arguably the most important bloom-forming cyanobacteria in freshwater systems, due to their global distribution, being reported on every continent except Antarctica [ 5 ], as well as their ability to produce toxins, which is known to have caused the shutdown of drinking water sources [ 6 , 7 ]. They form large colonies within amorphous mucilaginous sheathes [ 8 ] that constitute a niche for an abundant and diverse heterotrophic bacterial community [ 9 , 10 , 11 ] which together with Microcystis colonies comprise Microcystis -heterotrophic bacteria aggregates, hereafter Microcystis aggregates.

Microcystis aggregates constitute a unique physiochemical environment that likely supports proliferation of specific groups of bacteria. In addition to the rich variety of dissolved and particulate organic matter (DOM and POM) provided by Microcystis and their extracellular polymeric substance (EPS) matrix [ 12 ], potentially available as energy sources, the large size of aggregates can provide protection from zooplankton grazers [ 13 , 14 , 15 ], as well as from viral and bacterial threats [ 16 ]. Dissolved oxygen (DO) concentrations and pH within blooms fluctuate diurnally. For example, Chen and colleagues [ 17 , 18 ] measured DO fluctuations from 8.0 mg L −1 during the day to 0.5 mg L −1 at night and pH from 9.0 during the day to 7.3 at night. Moreover, Microcystis possesses gas vesicles [ 19 ] that provide buoyancy to the aggregates, allowing seasonal and diurnal migration to the water’s surface and thus access to sunlight [ 19 , 20 ].

This unique niche inhabited by heterotrophs surrounding phototrophs such as, but not limited to, Microcystis has been termed the phycosphere [ 21 , 22 ]. Some researchers have postulated that algal–bacterial mutualisms may enhance the growth conditions for both cyanobacteria and associated bacteria [ 22 , 23 ]. Further studies have suggested that cyanobacteria and associated bacteria may constitute functional interactomes [ 11 , 24 ] in which multiple microbial constituents contribute to complete metabolic pathways. Such relationships have been corroborated by demonstrating tighter network connections between Microcystis and heterotrophic bacteria within aggregates compared to those between Microcystis and free-living bacteria [ 25 , 26 ].

Previous work focusing on the diversity and function of isolates from cyanobacterial aggregates identified multiple novel species of aerobic anoxygenic phototrophic (AAP) bacteria [ 27 , 28 , 29 , 30 ] which have been hypothesized to play various roles in biogeochemical cycling within Microcystis bloom aggregates [ 25 , 31 , 32 , 33 ]. For example, nutrient bioassays have demonstrated that Microcystis blooms can become nitrogen (N) limited during summer months, with internal cycling necessary to sustain a bloom [ 34 , 35 ]. Studies based on microarrays and meta-transcriptomics have revealed denitrification and nitrogen fixation activities among associated bacteria in Microcystis blooms [ 32 , 36 ]. Other reported copy numbers of denitrification-related genes were strongly correlated with Microcystis biomass [ 37 ]. Phosphorus (P) is also needed for Microcystis growth, and cyanobacteria are often considered less effective than green algae in competing for P when its availability is limited [ 38 ], yet high concentrations of dissolved organic phosphorus (DOP) in laboratory culture experiments inhibited Microcystis growth [ 33 ]. Yuan et al. [ 31 ] postulated that phosphorus regeneration by associated bacteria within Microcystis aggregates is more important than P assimilated directly from outside the aggregate, suggesting the importance of associated bacteria in providing phosphorus for Microcystis growth. Sulfate (SO 4 −2 ) is the primary sulfur (S) source for Microcystis and can be directly reduced by Microcystis through assimilatory pathways to produce organic sulfur compounds [ 39 ]. Organic sulfur compounds, such as dimethyl sulfide and dimethyl trisulfide, are excreted by live Microcystis cells in addition to release upon cell death [ 40 ]. As these sulfur compounds are degraded, sulfide is released, acting as a potential toxin to cyanobacteria [ 41 ], with the possible inhibition of cyanobacterial growth [ 42 , 43 ]. These above studies, and others [ 44 , 45 ], provide the framework for understanding the critical role of the Microcystis microbiome in nutrient cycling within bloom aggregates. However, mechanisms, metabolic pathways, and predominant taxa involved in nutrient cycling within the Microcystis interactome are poorly understood. If indeed Microcystis and members of microbiome constitute an interactome, functionally cooperating in C, N, S, and P cycling dynamics, one would expect to find complementary components of the various metabolic pathways required for such cycling.

Here, we test the hypothesis that Microcystis and members of its microbiome possess complementary genes coding for metabolic pathways that support nutrient cycling within Microcystis aggregates. Using a 7-month metagenomic survey of free-living and aggregate-associated bacterial assemblages in Lake Taihu, China, we found that most bacteria enriched in Microcystis aggregates were AAP bacteria (9 of 13 genera), while AAP bacteria were present at lower relative concentrations in the surrounding water. Then, using a comparative genome analysis of 102 high-quality bloom-associated bacterial metagenome-assembled genomes (MAGs) from 10 lakes spanning four continents, we found that the biochemical pathways coded in AAP bacteria and Microcystis were potentially complementary for their roles in C, N, S, and P cycling within Microcystis bloom aggregates. Analysis of relative expression patterns of biochemical pathways from published metatranscriptomes revealed that biochemical pathways in AAP bacteria associated with C, N, S, and P cycling were among the most active processes during Microcystis blooms. Our analyses support hypothesized complementarity between Microcystis and members of its microbiome, particularly AAP bacteria, and provide ample targets for future research opportunities to better understand the Microcystis interactome.

Metagenome survey of Microcystis aggregate-associated bacteria in Lake Taihu

Frequent Microcystis blooms occur annually in Lake Taihu, China, especially in Meiliang and Zhushan Bays throughout late spring through autumn [ 46 ]. Microcystis bloom samples were collected monthly from the surface water at two sites in Meiliang Bay (site 1: 31°30′N, 120°11′E; site 2: 31°24′N, 120°10′E) and at two sites in Zushan Bay (site 3: 31°27′N, 120°01′E; site 4:31°23′N, 120°00′E) (Fig. S 1 ) from April to October in 2018. Samples were retrieved by dipping a sterile beaker off the side of a boat from the surface down to a depth of about 10 cm. Samples (2.5 L) from both sites of each bay were combined for subsequent manipulations. Subsamples were transferred into three 500-mL beakers and kept at room temperature for 10 min to allow cyanobacterial aggregates to float to the surface in each beaker. To obtain aggregate-microbiome bacteria, about 100 of the largest aggregates (1 ~ 2-mm diameter) of each sample in the floating aggregate layer were individually picked with a sterilized inoculation needle and were subjected to three successive sterile lake water washes (0.5 min each wash) [ 28 ] to detach free-living bacteria and loosely attached bacteria. The washed aggregates were combined and frozen prior to DNA extraction. The floating aggregate layer was then discarded, and the remaining 300 mL of water was filtered through a sterile 10-μm nylon net filter (Millipore) to remove any remaining aggregates [ 10 ]. The filtrate was filtered again through 0.2-μm pore-size filters to obtain the free-living bacteria fraction. Biomass on the filters was stored at − 80 °C before DNA extraction.

Temperature, DO, and pH were determined in situ using a YSI 6600 multiparameter water quality sensor. Diel changes in DO and pH in surface waters were measured in situ at site 1 in Meiliang Bay over a 24-h period from 10 to 10 AM on 10–11 August and 10–11 October 2018, corresponding to bloom peak and decline periods.

Genomic DNA was extracted using two methods in parallel to reduce possible extraction bias [ 47 ]: the UltraClean Soil DNA Isolation Kit (MoBio Laboratories, Carlsbad, CA, USA), and a phenol–chloroform protocol [ 48 ]. The concentration and purity of DNA were determined using a NanoDrop ND-2000 UV–Vis spectrophotometer (NanoDrop, Wilmington, DE, USA). DNA samples obtained by both methods were pooled in equal concentrations before further PCR and sequence analyses.

The 16S rRNA genes were amplified using 515F and 907R primers [ 49 ]. Sequencing of the 16S rRNA genes was performed using the Illumina MiSeq platform at Meiji Biotechnology Company (Shanghai, China). Amplicon sequences (16S) were deposited in the NCBI Sequence Read Archive under accession numbers (BioProject ID PRJNA985885) (Table S 1 ) and processed through the QIIME2 pipeline and its associated modules [ 50 ]. Briefly, an amplicon sequence variant (ASV) table was inferred using the DADA2 pipeline of QIIME2. Taxonomic annotation of ASVs was done using the SILVA database v138 [ 51 ]. The ASV table was filtered to remove mitochondria, chloroplasts, Eukarya, and cyanobacteria. Alpha-diversity indices for PD faith metrics and beta-diversity indices for weighted UniFrac distances were calculated with QIIME2 plug-ins using the filtered ASVs. Phylogenetic structure dissimilarities were compared for aggregate-associated and free-living assemblages using the weighted UniFrac distance and displayed in principal coordinates analysis (PCoA) plots. Differences between the two bacterial assemblages were tested using the Adonis test. ASV counts were aggregated to genus, and Welch’s t -test implemented in STAMP [ 52 ], to identify the bacterial genera ( p -value < 0.05 corrected by Benjamini–Hochberg FDR) for which relative abundances differed significantly between the aggregate-associated and the free-living communities.

Generality of AAP bacteria in Microcystis microbiomes

To examine whether AAP bacteria were generally important constituents of Microcystis blooms beyond Lake Taihu, we analyzed published Microcystis -bloom metagenomes from 10 global lakes [ 11 , 53 ]. The lakes spanned 90° latitude from Lake Aasee, Germany (52.0°N), to Lake Rotoehu, New Zealand (38.0°S), and 274° longitude from Castlerock Pond, USA (97.5°W), to Lake Rotoehu (176.5°E). General limnological information was included in previous studies [ 11 , 53 ]. All metagenomic sequences are available in GenBank (BioProject accession number PRJNA575023) [ 11 , 53 ] and were used here. Shotgun sequencing of the 10 global lakes and analysis, including quality trimming, removal of cyanobacterial reads, assembly, and MAG binning, is described in Cook et al. [ 11 ]. The quality of these bacterial MAGs was measured using CheckM v1.1.3. MAGs were further refined by manual removal of contamination using VizBin v1.0 [ 54 ]. High- and middle-quality MAGs were selected with a threshold of < 5% contamination and > 80% completeness.

Metabolic pathways inmicrobiome bacteria

A nonredundant Microbiome Genome Database was constructed using the 10 lake MAGs. It was constructed using “dereplicate” function of dRep v3.4.2 on the MAGs, based on > 30% aligned fraction and a genome-wide ANI threshold of 95% (− nc 0.3, − sa 0.95) [ 55 ], as described for the glacier [ 56 ] and human gut microbiome databases [ 57 ]. All MAGs were annotated using METABOLIC-G v4.0 [ 58 ] and DRAM v1.3 [ 59 ]. Based on the presence of photosynthetic gene clusters (PGCs) evidenced by the bch , puf , and acsF marker genes, a total of 49 MAGs with PGCs were categorized as AAP bacteria, and 53 lacking PGCs were categorized as non-AAP bacteria. MAGs were classified by GTDB-Tk v0.1.3 [ 60 ]. A total of 104 metabolic pathways were identified in these MAGs by METABOLIC-C v4.0 [ 58 ] to determine the presence and absence of pathways in AAP bacteria and non-AAP MAGs.

The pathways that exhibited significant differences between AAP and non-AAP MAGs were determined using a two-sample Kolmogorov–Smirnov test. This test compared the presence and absence of pathways in AAP and non-AAP MAGs, with a statistical significance threshold set at p  < 0.05.

Metabolic gene abundances in Microcystis and microbiome bacteria

To calculate the relative abundances of nutrient cycling genes within the aggregate community (i.e., microbiome +  Microcystis ), we added 12 complete Microcystis genomes to the Microbiome Genome Database, hereafter the Aggregate Genome Database. Nine of the Microcystis genomes were previously used in a pangenome analysis of Microcystis phylogeny [ 61 ], and three were recently released ( Microcystis aeruginosa FACHB-905 (accession number: CP089094.1), M. aeruginosa NIBR18 (CP086723.1) [ 62 ], and M. aeruginosa NIES-88 (AP024565.1). Gene prediction of the aggregate genome database was performed using Prodigal v2.6.3 with the “ − p meta” option. Gene functions were annotated using “kegg_annotation” function of Diting v0.9 [ 63 ] by querying the translated protein sequences against the KOfam database ( ftp://ftp.genome.jp/pub/db/kofam ) using hmmsearch [ 64 ] with KOfam suggested threshold values [ 65 ].

Specific gene abundances in the metagenomes were obtained by mapping the concatenated reads of all 10 lake samples back to the predicted gene sequences of the aggregate genome database using BWA-MEM with default settings [ 66 ] to generate sequence alignment map (SAM) files. The SAM files were used as input for pileup.sh of BBMap v38.22 with default settings [ 67 ] to calculate the average coverage of each gene. The GPM (genes per million) values for predicated genes were calculated as a proxy for gene abundance using the “table_of_ko_abundance_among_samples” function of DiTing v0.9 [ 63 ] with the following formula:

where GPM i is the relative abundance of gene i, b i is the copy number of gene i, L i is the length of gene i, X i is the number of times that gene i is detected in a sample (i.e., the number of reads in alignment), and j is the number of genes in a sample. This relative measure of abundance was developed for quantifying gene transcripts, as TPM (transcripts per million) [ 68 ], but is also equally useful in metagenomics studies [ 69 ]. GPM enables comparisons of gene abundances across different samples by normalizing for variations in sequencing length and depth, ensuring that each sample has the same number of total counts [ 68 ].

The GPMs were used to quantify relative abundances of specific biochemical pathways using formulae suggested by DiTing v0.9 [ 63 ]. For example, assimilatory sulfate reduction converting sulfite to sulfide has two known possible pathways: (1) the cysJI (K00380 and K00381) (encoding sulfite reductase (NADPH) flavoprotein alpha and beta-component)-mediated pathway [ 70 ] and (2) the sir (K00392) (encoding sulfite reductase (ferredoxin))-mediated pathway [ 71 ]. Thus, the relative abundance of the assimilatory sulfate reduction pathway is estimated by the following formula:

Due to the lack of relative abundance calculations for the P cycling pathways in DiTing v0.9 [ 63 ], functional genes related to P cycling were selected from within KEGG modules [ 72 ].

AAP and non-AAP bacterial metatranscriptomes

To investigate hypothesized functional roles of microbiome bacteria in Microcystis aggregates, we leveraged publicly available (NCBI SRA database and the MG-RAST [ 73 ] server) (Table S 2 ) Microcystis bloom metatranscriptomes from Lake Taihu and western Lake Erie and calculated the relative abundances of microbiome genes potentially involved in specific biochemical pathways. Metatranscriptomes of Lake Erie were collected at 7 sites in October 2013 (PRJNA262053), 14 sites in July and August 2014 (PRJNA354726), and a microcosm study in July 2019 (PRJNA823389). Metatranscriptomes of Lake Taihu were collected at one site in May 2015 (PRJNA359157) [ 32 ], one site from June to October 2015 (PRJNA664620), and one site from July to October 2016 (mgp103977) [ 74 ]. Because we lack specific microbiome genomes from the metatranscriptome studies, a general Microcystis microbiome genome set was created from 546 Microcystis bloom-associated microbiome genomes including MAGs and isolate genomes from western Lake Erie [ 75 ], Lake Taihu [ 44 ], Lake Champlain, and Pampulha reservoir [ 23 ]. Low-quality MAGs (completeness < 95%, contamination > 5%) were identified and removed using CheckM v1.1.3. The remaining MAGs were then dereplicated using dRep v3.4.2 with the same settings as for metagenome analysis described above to obtain a nonredundant microbiome genome set (Table S 3 ) consisting of 122 high-quality microbiome MAGs, which were annotated by DRAM v1.3 [ 59 ]. All genomes with PGCs were considered AAP bacteria genomes. This genome set was combined with the microbiome genome database created with the 10 global lake MAGs described above to generate an expanded microbiome genome database. Gene prediction and annotation for the expanded microbiome genome database were conducted using the same methods as the metagenome analysis described above.

The bloom transcriptomes from Lake Erie and Lake Taihu were then mapped to the genes in the expanded microbiome genome database and categorized as being derived from either AAP or non-AAP bacteria. Relative expression (TPM) of KEGG orthologs (KOs) and biogeochemical pathways were estimated as described above for relative gene abundances. The relative abundances of pathways from AAP and non-AAP groups were represented in box plots constructed through geom_boxplot and geom_jitter geom in the package in R v3.3.6. Significance tests for comparisons of pathway expression between the AAP and non-AAP groups were performed using a nonparametric pairwise Wilcoxon test ( p -value < 0.05 corrected by Benjamini–Hochberg FDR) within the stat_compare_means function in ggpubr v0.4.0.

As different metabolic processes are known to predominate during daytime and nighttime activities in Microcystis blooms [ 76 ], we leveraged publicly available (NCBI SRA database: SRP117911, SRP117914, SRP117915, SRP117922, SRP128942, SRP128945, and SRP128954) transcripts from a diel study of Microcystis blooms in western Lake Erie during late August 2014 (Table S 4 ) [ 76 ]. These transcripts were mapped against the expanded microbiome genome database and 12 complete Microcystis genomes for metagenome analysis described above and categorized as being derived from either AAP, non-AAP bacteria, or Microcystis as described above.

Microcystis microbiome bacteria in Lake Taihu

Chl a data indicated a rapid development of the cyanobacterial bloom in Lake Taihu, with peak abundance in August, followed by a decline in September and October (Table S 5 ). Chl a concentrations were linearly correlated with DOC concentrations in bloom samples (Fig. S 2 ). During the bloom peak, total nitrogen concentrations reached their lowest values (Table S 5 ). Diel changes of DO and pH within the bloom (Fig. S 3 ) during peak and decline phases likely influenced the expression of some biogeochemical pathways.

Microcystis 16S rRNA gene reads made up 65 ± 14% (mean ± standard deviation) of reads in the Lake Taihu aggregate-associated community during the 7-month study, while the free-living bacterial community contained only 2 ± 1% Microcystis reads. Non-cyanobacterial α-diversity was significantly lower ( p  < 0.001) in aggregates compared with free-living assemblages (Fig. S 4 A). β -diversity was also significantly different between aggregate and free-living assemblages (weighted UniFrac ( p  < 0.001) (Fig. S 4 B).

Thirteen genera, including 9 AAP bacterial genera ( Aquidulcibacter , Roseomonas , Porphyrobacter , Sandarakinorhabdus , Niveispirillum , Methylobacterium , Phreatobacter , Rhodobacter , and Gemmatimonas ) and 3 non-AAP genera ( Brevundimonas , Silanimonas , and Phenylobacterium ) along with uncultured Microscillaceae were enriched in Lake Taihu aggregates relative to free-living communities (Fig.  1 ). Seven genera (all non-AAP bacteria) were enriched in the free-living community relative to aggregate communities. AAP bacteria abundances in Lake Taihu aggregates comprised 17 to 36% of the non-cyanobacteria aggregate microbial community but only 0.01 to 9.8% of the free-living bacterial community (Fig. S 5 ).

Genera that differed significantly between the aggregate and free-living communities. The left-hand panel shows the relative abundance (percent of total) of each genus in free-living (blue) and aggregate (orange) samples, while the right-hand panel shows the mean differences in proportion between the two communities. AAP bacterial genera are in red type. Welch’s t -test was implemented in STAMP [ 52 ], with p -values corrected with Benjamini–Hochberg FDR method [ 52 ]

AAP bacteria in global Microcystis microbiomes

A total of 102 high-quality microbiome MAGs, including 49 AAP and 53 non-AAP MAGs, were recovered from the metagenomes of the global lake bloom aggregate samples. The MAGs were classified by GTDB-Tk [ 60 ], and about 75% of the AAP MAGs could be classified at the genera level. The majority of the AAP bacteria MAGs were classified [ 60 ] as Alphaproteobacteria (35 MAGs) and Betaproteobacteria (11 MAGs). Alphaproteobacteria AAP bacteria MAGs included Aquidulcibacter (5), Rhizobium (3), Rhodobacter (3), Bosea (2), Elioraea (2), Phreatobacter (2), Roseomonas (2), Porphyrobacter (1), and Methylobacterium (1) (Fig.  2 A). Among Betaproteobacteria AAP bacteria, five MAGs were unidentified members of family of Burkholderiaceae. The remaining MAGs were not identified, and of these, most similar reference genomes in the GTDB were verified to be AAP bacteria based on the presence of genes encoding anoxygenic photosynthesis. The majority of the non-AAP bacteria MAGs were Bacteroidetes (15 MAGs), Alphaproteobacteria (13 MAGs), and Gammaproteobacteria (9 MAGs) (Fig.  2 B).

The presence (filled) and absence (blank) of genes associated with C, N, S, and P cycling pathways in AAP ( A ) and non-AAP ( B ) bacterial MAGs derived from bloom sample metagenomes. The phylogenetic trees were built using UBCG [ 77 ]. MAGs were classified by GTDB-Tk v0.1.3 [ 60 ]. Star indicates AAP bacterial isolates from Microcystis aggregates collected from Lake Taihu. Carbon cycling genes: coxS , coxM , and coxL (small, medium, and large subunit of aerobic carbon-monoxide dehydrogenase), fdoG (formate dehydrogenase major subunit), fdoH (formate dehydrogenase iron-sulfur subunit), fdsD (formate dehydrogenase delta subunit), fdoI (formate dehydrogenase gamma subunit), fdwB (formate dehydrogenase beta subunit). Sulfur cycling genes: soxA (sulfur-oxidizing protein SoxA), soxX (sulfur-oxidizing protein SoxX), soxB ( sulfur-oxidizing protein SoxB), soxY (sulfur-oxidizing protein SoxY), soxZ (sulfur-oxidizing protein SoxZ), soxC (S-disulfanyl-L-cysteine oxidoreductase SoxC), soxD (S-disulfanyl-L-cysteine oxidoreductase SoxD), tsdA (thiosulfate dehydrogenase), fccB (sulfide dehydrogenase flavoprotein chain), fccA (cytochrome subunit of sulfide dehydrogenase), sqr (sulfide:quinone oxidoreductase), soeA , soeB , soeC (sulfite dehydrogenase (quinone) subunits SoeA, SoeB, and SoeC). Nitrogen cycling genes: narG , narH , narI (alpha, beta, and gamma subunit of nitrate reductase/nitrite oxidoreductase), napA (nitrate reductase (cytochrome)), napB (nitrate reductase (cytochrome), electron transfer subunit), nrfH (cytochrome c nitrite reductase small subunit), nrfA (nitrite reductase (cytochrome c-552)), nirB (nitrite reductase (NADH) large subunit), nirD (nitrite reductase (NADH) small subunit), nirK (nitrite reductase (NO forming). Phosphorus cycling genes: phnG (carbon-phosphorus lyase core complex subunit), phnM (alpha-D-ribose 1-methylphosphonate 5-triphosphate diphosphatase), and phoX (alkaline phosphatase). Cytochrome c oxidase genes: caa3-type cytochrome c oxidase ( coxABCD ). cbb3-type cytochrome c oxidase ( cooNOPQ and cooNQ )

Metabolic pathways in the Microcystis interactome

The presence of caa3 and cbb3 -type cytochrome c oxidases in most MAGs indicated that abundant microbiome bacteria were mostly obligate or facultative aerobic bacteria. Of the 104 biochemical pathways identified in the microbiome genome database, 18 pathways occurred in significantly more AAP bacteria than non-AAP bacteria (Fig.  3 ; using the Kolmogorov–Smirnov test, P  < 0.05). For example, the carbon monoxide (CO) oxidation pathway ( coxSML ) occurred in 31 of 49 AAP MAGs (63%) but in only one of 53 non-AAP MAGs (2%) (Fig.  2 ). More AAP bacteria had genes encoding pathways of amino acid utilization, oxidation of CO, formate, thiosulfate, sulfide, and sulfite, reduction of nitrate and nitrite to ammonia, DHPS (2,3-dihydroxypropane-1-sulfonate) catabolism, and organic P mineralization, while more non-AAP bacteria had genes encoding pathways of denitrification, including genes for reduction of nitric oxide and nitrous oxide (Fig.  3 ). AAP bacteria containing genes for oxidation of CO, formate, and reduced S are also capable of reducing nitrate and nitrite via ammonification. coxSML genes (oxidation of CO) and S oxidation genes encode aerobic enzyme complexes, while formate oxidation involves an anaerobic enzyme complex. These findings suggest that some AAP bacteria have versatile lifestyles, as they can carry out carbon monoxide assimilation and S oxidation in the presence of oxygen and formate oxidation with nitrate and iron as electron acceptors in the absence of oxygen. The most abundant AAP bacterium, Roseomonas , possessed genes encoding metabolic pathways for obtaining energy from organic carbon, CO, and sulfide oxidation, and sunlight via anoxygenic photosystems (Fig.  2 A), as well as for being able to switch between aerobic respiration, anaerobic respiration, and fermentation.

Pathway presence (represented as a percentage within the community) in AAP bacteria MAGs and non-AAP bacteria MAGs within Microcystis bloom samples of global lakes. Kolmogorov–Smirnov test, p  < 0.05 was used to determine whether representation in genomes was significantly different. Stars indicated coverage of pathways was significantly different between AAP and non-AAP MAGs. Specific pathways were present based on key genes suggested by METABOLIC-C v4.0 [ 58 ]

Metabolic gene abundances in the Microcystis interactome

To aid in understanding the potential for interactions between Microcystis and associated bacteria, relative abundances (expressed as GPM) of metabolic genes in the 10 lake metagenomes were determined (Fig.  4 ). For each lake, 85.5 to 95.1% of microbiome bacteria reads were mapped onto the Aggregate Genome Database, indicating that the Aggregate Genome Database was representative of the microbiota present during blooms.

Biochemical pathways for microbial synthesis and catabolism of carbon ( A ), nitrogen ( B ), phosphorus ( C ), sulfur ( D ), and organic sulfur ( E ) metabolites in Microcystis (blue), AAP (red), and non-AAP (yellow) from global bloom samples. The genes per million reads (GPM) were calculated to understand the importance of each process in the biogeochemical cycles. The size of the pie chart in panels is proportional to the relative abundance of each gene involved in the pathway. rTCA, reversal citric acid cycle; CBB, Calvin–Benson–Basham; WL, Wood–Ljungdahl; ED, Entner-Doudoroff; 3HB, 3-hydroxypropionate bicycle. DSR, dissimilatory sulfate reduction; ASR, assimilatory sulfate reduction. Key genes involved in the pathways are shadowed gray. The key genes involved in conversion of acetaldehyde to ethanol and TCA cycles are described here ( https://github.com/xuechunxu/DiTing/blob/master/Pathway_formulas.txt )

Carbon cycling

For CO 2 fixation, Microcystis uses the Calvin–Benson–Bassham cycle (CBB), and AAP bacteria appear to use the 3-hydroxypropionate bicycle (3-HB). No reverse citric acid cycle or Wood–Ljungdahl cycles were identified (Fig.  4 A). However, only five of six marker genes of the 3-HB cycle were detected in the communities, and the key gene encoding propionyl-CoA carboxylase was not detected, suggesting that 3-HB cycle was incomplete in the aggregate AAP bacteria. The presence of genes encoding L-lactate dehydrogenase and alcohol dehydrogenase in Microcystis genomes suggests that Microcystis can also produce lactic acid and ethanol during fermentation. A previous study has also documented the production of acetate and ethanol as fermentation products [ 78 ]. If produced, the fermentation products may be further utilized by associated bacteria. In global metagenomic data, genes involved in acetate/ethanol catabolism, including the genes encoding acetate kinase (AAP: 56.6 GPM vs non-AAP: 8.6 GPM), phosphotransacetylase (AAP: 49.1 GPM vs non-AAP: 4.2 GPM), and isocitrate lyase (AAP: 56.9 GPM vs non-AAP: 28.3 GPM) [ 79 ], were enriched in AAP bacterial communities. C1 metabolism pathways, including formate production and/or oxidization when anoxic conditions are present and CO oxidation under oxic conditions, were enriched in AAP bacteria (Fig.  4 A). Formate metabolism was indicated by the presence of formate C-acetyltransferase ( pflD ), which catalyzes formate production during pyruvate degradation and formate dehydrogenase ( fdh/fdo ), catalyzing formate oxidation to CO 2 and H 2 .

Nitrogen cycling

The dominant nitrogen cycling pathways were assimilatory nitrate and nitrite reduction in Microcystis (Fig.  4 B). AAP bacteria were enriched in the dissimilatory nitrate reduction pathways, including nitrate reduction to nitrite and nitrate reduction to ammonium (DNRA). However, there is no correlation between the abundance of anoxygenic photosynthesis and the pathways involved in nitrogen cycling. This lack of a relationship may be because bacteria in some lakes (Aasee, FP23, and Villerest) had high relative abundances of anoxygenic photosynthesis genes but had none of the DNRA genes, including narGHI , nirBD , or nrfAH genes (Fig. S 6 ). In those lakes, nitrate reduction (denitrification) pathways were primarily expressed by non-AAP bacteria. No genes encoding anammox, including hzsABC and hdh , were identified in the Aggregate Genome Database or contigs assembled from each metagenome.

Phosphorus cycling

Microcystis had the most abundant P utilization pathway genes, including orthophosphate transport ( pstSCAB ), polyphosphate synthesis ( ppK ), and hydrolysis ( ppA ). Phytoplankton are known to store inorganic P as polyphosphate (PolyP) in cells when P is abundant and break it down when P is limiting [ 80 ]. Three bacterial alkaline phosphatase families ( phoA , phoD , and phoX ) were identified, and over 48% of phoX gene reads, common among cyanobacteria [ 81 ], were present in Microcystis . However, phoA and phoD were only associated with AAP and non-AAP bacteria (Fig.  4 C). Organophosphonate mineralization genes ( phnGHIL , phnJ , and phnM ) were mainly found in AAP bacteria (Fig.  4 C). Interestingly, methane can be produced by C–P lyase complex ( phnJ ), indicating that AAP bacteria could also be involved in methane production.

Sulfur cycling

Assimilatory sulfate reduction ( cysJI ) and cysteine biosynthesis ( cysE ) were the most abundant genes involved in sulfur cycling observed in Microcystis and microbiome genomes, with over 98% of cysJI genes and 70% of cysE genes in the metagenome derived from Microcystis (Fig.  4 DE). This indicates that Microcystis may be capable of assimilatory sulfate reduction to sulfide and incorporation of sulfide into the amino acids methionine and cysteine. The primary S-cycling function of associated bacteria appears to be S oxidation. AAP bacteria had genes relating to several oxidation processes, including sulfide ( fccAB ), thiosulfate ( sox ), and sulfite oxidation ( soeABC ). AAP bacteria were likely the dominant players in the catabolism of dissolved organic sulfur (DOS) metabolites. The sulfonate compound 2,3-dihydroxypropane-1-sulfonate (DHPS) is one of the most abundant organic sulfur compounds in the biosphere [ 82 ]. DHPS catabolase ( hpsN ) was the most abundant gene in the DOS catabolism pathway among AAP bacteria.

AAP bacteria gene expression during nutrient cycling

The relative expression data comparing AAP bacteria and non-AAP bacteria in Lake Erie and Taihu during blooms were generally similar to the corresponding relative abundances obtained by the metagenome-based community analysis. The metatranscriptomic analysis showed that Microcystis had predominantly assimilatory pathway transcriptional expression [ 32 , 74 , 83 ]. Relative to non-AAP bacteria, AAP bacteria produced relatively higher levels of transcripts for carbon (CO oxidation and formate oxidation), sulfur (sulfide, thiosulfate, and sulfite oxidation, DOS catabolism), and phosphorus metabolism (C-P metabolism), while non-AAP bacteria displayed higher levels of transcripts involved in nitrous oxide reductase ( nosZ ) (Fig.  5 ). In addition, both AAP bacteria and non-AAP bacteria had low transcript abundance for genes associated with nitrogen metabolism compared to the other nutrient metabolisms (Fig.  5 ).

Relative transcript abundance of biogeochemical pathways in metatranscriptomic samples from Lakes Erie and Taihu (Table S 2 ). The transcripts per million (TPM) was calculated. The interquartile range is represented within the box. The lower and upper hinge of the box represents the 25th and 75th percentiles, respectively. Stars indicate that the relative abundance of the pathways varied significantly between AAP and non-AAP groups (pairwise Wilcoxon test with p -values corrected with Benjamini–Hochberg FDR method). Key genes for each pathway are given. Metatranscriptomic data are publicly available from the NCBI SRA database, courtesy of [ 32 , 74 , 83 ], and the accession numbers and additional information about the metatranscriptomes are shown in Table S 2

Diel transcriptional patterns of biogeochemical pathway genes from Microcystis , AAP bacteria, and non-AAP bacteria in western Lake Erie during late August 2014 were also observed (Fig.  6 ). Transcripts involved in the production of ethanol, acetate, and lactate from Microcystis increased primarily during the day. The relative abundances of anoxygenic photosynthesis transcripts and formate oxidation transcripts from AAP bacteria increased primarily at night. Conversely, the aerobic carbon monoxide oxidation transcript abundance from AAP bacteria increased during the day, yielding maximum relative abundances at 16:00 h. Genes for the DNRA pathway showed higher relative transcript abundances during the day. Phosphorus acquisition and uptake ( pho , ppa ) by Microcystis were found to be relatively constant over the entire period. However, organophosphonate metabolism ( phnJ ) from AAP bacteria was highly upregulated during the day, and their transcriptional expression rapidly decreased at night. For sulfur metabolism, the assimilatory pathways ( cysJI and cysE ) were expressed by Microcystis and showed higher relative transcript abundances during the day . The assimilatory sulfate reduction pathway ( cysJI ) exhibited higher relative transcript abundances at night. Conversely, the biosynthesis of cysteine ( cysE ) displayed higher relative transcript abundances during the day. The genes involved in inorganic sulfur oxidation ( soeABC , sox ) and organic sulfur catabolism ( hpsN , suyAB ) were expressed almost exclusively by AAP bacteria, and their transcript abundances increased during the day. The fccAB gene involved in sulfide oxidation was expressed by both AAP bacteria and non-AAP bacteria in those samples, and their transcript abundances also increased during the day.

Diel transcriptional levels (TPM) of genes for microbial synthesis and catabolism of carbon ( A ), nitrogen ( B ), phosphorus ( C ), and sulfur ( D ) in Microcystis (green), AAP (red), and non-AAP (yellow). Gray shading indicates periods between sunset and sunrise. Samples were collected in western Lake Erie in late August 2014. For more detailed information about the samples, please refer to Table S 4

The microenvironment surrounding algae and algal colonies in which bacteria were often observed as being abundant was first termed the “phycosphere” by Bell and Mitchell [ 21 ]. Such associations between bacteria and bloom-forming algae, particularly cyanobacteria, are well-documented and have often been speculated as being symbiotic (e.g., [ 22 , 84 ]) with the associated bacteria potentially representing a microbiome analogous to the microbiome concept described for humans [ 85 ], soils [ 86 ], and coral reefs [ 87 ]. The Microcystis phycosphere possesses unique characteristics. Firstly, the Microcystis aggregates shield inhabiting bacteria from grazers [ 14 , 16 ], which is likely important as AAP bacteria are relatively large and therefore more susceptible to protist grazing than other smaller bacteria [ 88 ]. Due to intense top-down pressure, the number of AAP bacteria in waters is relatively low [ 89 ]. However, with the protection of the aggregates, we observed that the proportion of AAP bacteria in global bloom samples can exceed 20% of the non-cyanobacterial bacteria, whereas the proportion of AAP bacteria in surrounding water is usually less than 10% of the non-cyanobacterial community (Fig. S 5 ). Secondly, Microcystis produces reduced organic nutrients that bacteria can utilize to gain energy. These reduced organics include a variety of organic sulfur metabolites [ 90 ], such as cysteine and DHPS, which could provide energy equivalent to, or greater than, organic carbon compounds during oxidative processes [ 91 ]. Comparative genomic analysis has shown that genes involved in DOS catabolism and oxidation of reduced sulfur metabolites are present in fast-growing AAP bacteria (Fig.  3 ). Thirdly, Microcystis creates a distinctive environment with large fluctuations in DO and pH (Fig. S 3 ), which further selects for specific bacteria. Genes involved in respiratory and fermentative processes are ubiquitous in associated bacterial genomes (Figs.  2 and  3 ) and are highly responsive to the diel environmental fluctuations induced by Microcystis activities (Fig.  6 ). This observation suggests AAP bacteria in bloom aggregates can adjust to environmental fluctuations created by Microcystis activities by switching between aerobic and anaerobic processes. Lastly, Microcystis possesses gas vesicles that provide buoyancy to the aggregates and thus higher access to sunlight. This access may provide advantages to photoheterotrophs, such as AAP bacteria, containing bacteriochlorophyll with maximal absorption at ~ 870 nm. Bacteriochlorophyll-based photosynthesis under infrared light has been shown to significantly reduce respiration and enhance the assimilation of organic compounds by AAP bacteria [ 92 ]. Thus, Microcystis buoyancy may provide AAP bacteria a mechanism for maximizing photosynthesis while reducing respiration. Cook et al. [ 11 ] recently postulated that cyanobacteria-microbiome associations constitute complex interactomes (sensu [ 93 ]), consisting of one to several dominant cyanobacterial species and multiple bacterial taxa, which have coevolved to form a community of mutualistic and synergistic species, each with unique metabolic capabilities that are critical to the growth, maintenance, and demise of cyanobacterial blooms. As temperatures increase during the late spring and summer, Microcystis quickly forms a dense layer of biomass on the surface [ 1 ], leading to depletion of N and/or P [ 34 ]. As inorganic nutrients are depleted, Microcystis must rely on microbial partners to satisfy needs for essential nutrients. Knowledge of the biogeochemical interactions between Microcystis and its microbiome is key to understanding mechanisms that allow sustained growth throughout the season.

AAP bacteria populations in the aggregates

Initial experiments looking at the ecology of the bloom showed a significantly decreased richness in the aggregate community relative to the free-living community (Fig. S 4 ). This observation, which has been previously reported [ 9 , 25 ], suggests that physical, chemical, or biological factors within the aggregates restrict or enrich the microbiota of specific taxonomic or functional groups. Beta-diversity measures also showed significant differences between aggregates and free-living samples for the weighted UniFrac metric (Fig. S 4 ), suggesting substantial differences in community composition between the two groups.

The nine groups of AAP bacteria (confirmed by the presence of genes encoding anoxygenic photosynthesis in MAGs) that were enriched in Microcystis aggregates (Figs.  1 and  2 ) included two novel genera, suggesting further unknown diversity. Nevertheless, our finding that specific AAP bacteria were consistently present in high abundance across all global samples (Fig. S 5 ) suggests the potential existence of a core functional microbiome comprised of AAP bacteria across Microcystis blooms, in line with the notion that a core Microcystis microbiome may not be defined at the species or genus level [ 23 , 75 ].

Biogeochemical interactions between Microcystis and AAP bacteria

During dark anoxic conditions and light/dark cycle, Microcystis was found to ferment stored sugar into ethanol, acetate, and lactate [ 78 , 94 , 95 ]. Transcripts involved in the production of ethanol, acetate, and lactate from Microcystis increased primarily during the day (Fig.  6 ), in line with the previous physiological study [ 95 ], indicating the presence of anoxic micro-niches within the bloom during the day. However, fermentation products, when they accumulate, can inhibit Microcystis growth [ 78 , 96 ]. Genes involved in ethanol catabolism and formate oxidation were enriched in AAP bacterial communities, suggesting that AAP bacteria obtained energy by degrading and detoxifying the fermentation product. In addition, the enriched β-xylosidase and rhamnosidase observed in AAP bacterial genomes likely are involved in degradation of cyanobacterial EPS known to contain rhamnose and xylose [ 12 ]. Interestingly, an associated AAP bacterium, Niveispirillum cyanobacteriorum , produces β-galactosidase, a catabolic enzyme with potential functions in polysaccharide degradation and not present in the related non-AAP species Niveispirillum fermenti and Niveispirillum irakense [ 27 ], indicating further adaptation associated with living in the phycosphere.

The most abundant aerobic pathway enriched and expressed in AAP bacterial communities is for CO oxidization. coxSML genes transcribing proteins involved in CO oxidation are present in many AAP bacteria, including the Roseobacter group [ 97 , 98 ]. A previous study indicated that AAP bacteria could use light and CO oxidation as complementary energy sources to better survive under severe energy limitations [ 99 ]. The origin of CO remains unclear.

Microcystis blooms are generally nitrogen (N) limited during summer months [ 34 , 100 ] and the most abundant and most highly expressed genes involved in N cycling present in Microcystis encode nitrogen assimilatory pathways. Dissimilatory nitrate reduction to ammonium (DNRA) by AAP bacteria is therefore likely to be an important source of NH 4  + -N for Microcystis . Under anoxic conditions, biologically available N can be removed from ecosystems through anaerobic ammonium oxidation (anammox) or denitrification, whereas DNRA acts to conserve N within the system. Anammox often occurs at the interface between surface water and sediment porewater and is limited to areas that are relatively low in labile carbon, which often is not the case for near-surface freshwater sediments that support high biological productivity [ 101 ]. Furthermore, our data analysis did not identify any genes associated with anammox. Denitrification is also likely an important process within blooms with denitrification rates as high as 392 μmol m −2  h −1 reported in Lake Taihu blooms at high TN concentrations (6.58 mg N L −1 ), a rate much higher than observed in the sediments [ 18 ]. Our data indicated that denitrification genes were encoded and expressed in the majority of non-cyanobacterial non-AAP bacteria. For DNRA to be favored over denitrification, a high level of electron donors is needed [ 102 ]. The higher abundances of genes mediating organic C decomposition and C1 and S compound oxidation in AAP bacteria provide support for this concept.

DOP is a major component of the P pool in aquatic ecosystems and includes phosphomonoesters (-C-O-P) and phosphonates (C-P) [ 103 ]. The most abundant P cycling genes derived from Microcystis encode dissolved inorganic phosphate (DIP) assimilation ( ppa and ppk ) and transporter ( pst ) genes. Although Microcystis alkaline phosphatase activity was detected [ 33 ], Microcystis growth is thought to be inhibited by high concentrations of DOP, indicating that Microcystis most likely cannot metabolize DOP present at high levels. Associated bacteria have various DOP transporters, carbon-phosphorus lyases, and alkaline phosphatases, likely degrading DOP and providing DIP to Microcystis . Based on the presence and expression of phn genes in AAP bacteria, they likely play a significant role in P mineralization and methane production in Microcystis aggregates. phn genes are responsible for the process of demethylation of methylphosphonates, which can occur under aerobic conditions [ 104 ].

Microcystis is known to produce reduced sulfur organic compounds, which can also be self-toxic [ 43 ]. The primary roles of AAP bacteria in sulfur metabolism appear to be in catabolism of organic sulfur compounds and oxidation of reduced inorganic sulfur compounds. DHPS degradation pathways were previously observed in marine AAP bacteria genomes [ 105 ]. Our analysis showed that DHPS metabolic pathways were also present, converting DHPS to sulfite and pyruvate, and were highly expressed in many freshwater AAP bacteria. Sulfite could be further oxidized by AAP bacteria encoding sulfite-oxidizing enzymes ( soeABC ). Although oxidation of reduced sulfur compounds is usually thought to be carried out by anaerobic phototrophic sulfur bacteria [ 106 ], AAP bacteria (which are aerobic) appear to be capable and likely important in several S oxidation processes. Strong diel fluctuations in DO within aggregates and high transcript abundances of genes involved in inorganic sulfur oxidation ( soeABC , sox ) and organic sulfur catabolism ( hpsN , suyAB ) during the day indicate that sulfur oxidizers were active under aerobic conditions. Many AAP bacteria can oxidize inorganic sulfur compounds growing lithotrophically under aerobic conditions [ 107 ]. The ability to oxidize thiosulfate appears to be especially widespread in AAP bacteria species [ 108 ].

Based on the combined results of metagenomic and metatranscriptomic analyses, biogeochemical pathway reconstruction, and diel expressional analysis of Microcystis and its associated microbiome, we have proposed a biogeochemical network between Microcystis and the AAP bacteria-containing microbiome (Fig.  7 ). The network shows how the interactions between Microcystis and the microbiome can support the bloom when nutrients are limited. Metabolic dependencies can drive species co-occurrence in diverse microbial communities (sensu [ 109 ]), and cross-feeding may expand the metabolic niche of bacteria [ 110 ]. Our results can also help inform the development of new strategies for the mitigation of bloom events. For example, the sulfur-cycling-enabled mutualism between Microcystis and AAP bacteria highlights the importance of reducing S input as a potential strategy for the mitigation of bloom events, in addition to reducing N and P input. Elevated sulfate concentrations lead to increased sulfide production by Microcystis and phosphorous mobilization [ 111 , 112 ]. This, in turn, promotes biomass formation and formation of reduced sulfur by Microcystis [ 90 ], providing ample reduced sulfur as an energy source for AAP bacteria and improving internal nutrient cycling within aggregates. However, while support for our hypotheses is derived from metagenomic and metatranscriptomic analyses, further investigation through metabolomic studies will be essential for testing the hypotheses regarding shared or complementary pathways. Additionally, the Microcystis -microbiome biogeochemical network is a complex interactome that will need much more study to unravel its complexity.

Schematic diagram of the biogeochemical network within Microcystis and AAP bacteria during bloom. The biogeochemical activities are displayed in a relative manner using different line thicknesses, based on the relative abundance of biochemical pathways from metagenomes shown in Fig.  4 and metatranscriptomes shown in Fig.  5

Availability of data and materials

The raw sequencing data were submitted to the NCBI SRA database under the accession ID PRJNA985885. The genomes of AAP isolates in Microcystis aggregates from Lake Taihu were submitted to the NCBI SRA database under the accession ID PRJNA427797, PRJNA427794, PRJNA427795, PRJNA427804, PRJNA395960, and PRJNA382246.

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Acknowledgements

We thank members of the Plankton Ecology and Limnology Lab for helpful feedback during discussions.

This work was supported by the US National Science Foundation (Grant DEB-1831061 to K. D. H. and L. R. K.) and the National Key Research and Development Program of China (Grant 2018YFA0903000 to H. C.), and the Natural Science Foundation of Jiangsu Province of China (Grant BK20191508 to H. C.).

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Haiyuan Cai, Christopher J. McLimans, Lee R. Krumholz & K. David Hambright

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Conceptualization: H.C. and K.D.H. Bioinformatics: H.C. and C.J.M. Interpretation: H.C., C.J.M., H.L., F.C., L.R.K., and K.D.H. Writing—original draft: H.C. Writing—review and editing: H.C., C.J.M., H.L., F.C., L.R.K., and K.D.H.

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Additional file 1:.

Fig. S1. Map of Lake Taihu and the sampling sites at Meiliang Bay and Zushan Bay, and Taihu Laboratory for Lake Ecosystem Research (TLLER). Fig. S2. Linear relationship between concentrations of DOC and Chl a of water samples in Lake Taihu. Data are based on 8 samples from site 1 at Meiliang Bay in September 2018. Fig. S3. Diel variation of DO and pH during a Microcystis bloom. Samples were collected from 51 site 1 in Meiliang Bay, Taihu, over a 24-h period from 10 to 10 AM on 10–11 August and 10–11 October 2018. Data are mean ± standard deviation (SD) ( n  = 3). Fig. S4. Alpha- and beta-diversity of samples from Lake Taihu. Free-living communities are displayed in blue and aggregate communities in orange. PD faith is used as an index for alpha diversity (A). Significant differences between the groups are indicated with asterisks (*** p  < 57 0.001). For beta-diversity (B), PCoA plot of the weighted UniFrac measures is shown. The x- and y-axes represent the first and second principal coordinates with the proportion of variance. Both diversity measures show significant differences between free-living and aggregate 60 communities. Fig. S5. Relative abundances of AAP bacterial genera in non-cyanobacterial communities in bloom samples from Lake Taihu (A) and ten global lakes (B). The sample IDs in Lake Taihu are shown in Table S1. Fig. S6. Relationships between gene abundance of anoxygenic photosystem pathways and important C, N, S, and P cycling pathways. Instead of using genes from MAGs, genes were derived from contigs co-assembled by metaSPAdes v3.15.4 using the metagenome data from each lake with Microcystis reads removed. Two biological replicates were obtained for each sample. Gene identification, annotation, and KO (KEGG Orthology) analysis were described in the text. Then reads of the ten lake metagenomes were mapped to genes derived from the contigs, and calculated GPMs. The GPMs were the input to calculate the relative abundance of pathways of each metagenome using formulae suggested by DiTing v0.9 [5]. Table S1. Collection date, location, sample type, and accession information for Lake Taihu 22 samples. Table S2. Source, location, date of collection and accession information for Lake Erie and Taihu transcriptome samples. Table S3. Taxonomic, completeness and contamination data for non-redundant microbiome MAGs. Table S4. Diel Bloom transcriptomes from Lake Erie. Table S5. Environmental variables of Meiliang Bay (M) and Zushan Bay (Z) in Lake Taihu. Chl a concentrations indicated that the 38 Microcystis bloom grew rapidly peaking between August and September, and the bloom began to decline in October. The pH in bloom 39 samples (from August to October) ranged from 8.0 to 10.0. The mass ratios of total nitrogen (TN) to total phosphorus (TP) ranged from 40 6.7 to > 31.8, but were lowest in the months of summer and fall, suggesting the Microcystis bloom was potentially N-limited.

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Cai, H., McLimans, C.J., Jiang, H. et al. Aerobic anoxygenic phototrophs play important roles in nutrient cycling within cyanobacterial Microcystis bloom microbiomes. Microbiome 12 , 88 (2024). https://doi.org/10.1186/s40168-024-01801-4

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Potential Early Biomarker for Alzheimer’s Disease Identified: A ScienceAlert Update

D espite the absence of a cure for Alzheimer’s disease, scientists have made a promising discovery: a potential biomarker that could signal the presence of the disease before any symptoms manifest. This discovery could pave the way for early intervention treatments and provide deeper insights into the disease’s progression.

The biomarker, a microRNA molecule known as miR-519a-3p, was identified by a research team from the Institute for Bioengineering of Catalonia (IBEC) and the University of Barcelona. The researchers believe that this biomarker could serve as an important early warning tool for Alzheimer’s disease.

The findings from the study, which point to elevated levels of miR-519a-3p in individuals with Alzheimer’s, were led by neuroscientist José Antonio del Río of IBEC. He emphasizes the usefulness of detecting this microRNA for improving the accuracy of early-stage diagnosis.

MicroRNA molecules such as miR-519a-3p are small, non-coding RNA fragments that aid in the regulation of protein production within cells. These molecules are stable throughout the body and readily detectable in biological fluids, making them ideal candidates for biomarkers.

Notably, miR-519a-3p is connected with the cellular production of prion protein (PrP C ), which was already suspected to play a role in the early stages of Alzheimer’s. Interestingly, the concentration of PrP C seems to fall off as Alzheimer’s advances.

Through research analyzing brain tissue from deceased Alzheimer’s patients and subsequent chemical tests, it was determined that miR-519a-3p is instrumental in lowering the production of PrP C .

The possibility of miR-519a-3p being an indicator of early Alzheimer’s is backed by solid evidence, though it is not yet confirmed. To ensure the specificity of miR-519a-3p as an Alzheimer’s marker, neuroscientist Rosalina Gavín points out the importance of confirming that this biomarker does not fluctuate with other neurodegenerative conditions.

Significant progress in various facets of Alzheimer’s research has been made, including understanding how PrP C decreases as the disease worsens and how to potentially employ this in early detection. This is just one of the many early warning signals identified by scientists in recent times, eventually leading to a combined methodology for early Alzheimer’s detection.

Future research aims include validating miR-519a-3p as a biomarker within blood samples from patient cohorts to eventually integrate it into the clinical diagnosis process, as advocated by neuroscientist Dayaneth Jácome from IBEC.

The study has been published in the journal Biochimica et Biophysica Acta (BBA) – Molecular Basis of Disease .

FAQ Section

What is a biomarker.

A biomarker is a measurable substance in the body that is indicative of some biological state or condition. It can be used to detect or monitor diseases, measure the effects of treatments, or assess the health of an individual.

Why is the early detection of Alzheimer’s disease important?

Early detection of Alzheimer’s allows for the possibility of slowing the progression of the disease through early intervention treatments, as well as providing the opportunity for patients and their families to plan for the future.

Is miR-519a-3p found only in Alzheimer’s patients?

Current research suggests that miR-519a-3p levels are specifically altered in Alzheimer’s disease but not in other neurodegenerative diseases. This specificity makes it a potentially powerful biomarker for early diagnosis.

What is the next step in the research involving miR-519a-3p?

The next phase is to validate miR-519a-3p as a biomarker in blood samples from larger patient cohorts to confirm its effectiveness in the clinical diagnosis of Alzheimer’s disease.

The discovery of microRNA molecule miR-519a-3p as a potential biomarker offers hope for the early diagnosis and treatment of Alzheimer’s disease. This is an exciting development as it provides a non-invasive way to potentially detect the disease before the onset of symptoms. More research is needed to validate these findings and translate them into a clinical setting, but the prospects for earlier detection of Alzheimer’s are promising.

Are Markups Driving the Ups and Downs of Inflation?

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FRBSF Economic Letter 2024-12 | May 13, 2024

How much impact have price markups for goods and services had on the recent surge and the subsequent decline of inflation? Since 2021, markups have risen substantially in a few industries such as motor vehicles and petroleum. However, aggregate markups—which are more relevant for overall inflation—have generally remained flat, in line with previous economic recoveries over the past three decades. These patterns suggest that markup fluctuations have not been a main driver of the ups and downs of inflation during the post-pandemic recovery.

In the recovery from the pandemic, U.S. inflation surged to a peak of over 7% in June 2022 and has since declined to 2.7% in March 2024, as measured by the 12-month change in the personal consumption expenditures (PCE) price index. What factors have been driving the ups and downs of inflation? Production costs are traditionally considered a main contributor, particularly costs stemming from fluctuations in demand for and supply of goods and services. As demand for their products rises, companies need to hire more workers and buy more intermediate goods, pushing up production costs. Supply chain disruptions can also push up the cost of production. Firms may pass on all or part of the cost increases to consumers by raising prices. Thus, an important theoretical linkage runs from cost increases to inflation. Likewise, decreases in costs should lead to disinflation.

Labor costs are an important factor of production costs and are often useful for gauging inflationary pressures. However, during the post-pandemic surge in inflation, nominal wages rose more slowly than prices, such that real labor costs were falling until early 2023. By contrast, disruptions to global supply chains pushed up intermediate goods costs, contributing to the surge in inflation (see, for example, Liu and Nguyen 2023). However, supply chains have more direct impacts on goods inflation than on services inflation, which also rose substantially.

In this Economic Letter , we consider another factor that might drive inflation fluctuations: changes in firms’ pricing power and markups. An increase in pricing power would be reflected in price-cost markups, leading to higher inflation; likewise, a decline in pricing power and markups could alleviate inflation pressures. We use industry-level measures of markups to trace their evolving impact on inflation during the current expansion. We find that markups rose substantially in some sectors, such as the motor vehicles industry. However, the aggregate markup across all sectors of the economy, which is more relevant for inflation, has stayed essentially flat during the post-pandemic recovery. This is broadly in line with patterns during previous business cycle recoveries. Overall, our analysis suggests that fluctuations in markups were not a main driver of the post-pandemic surge in inflation, nor of the recent disinflation that started in mid-2022.

Potential drivers of inflation: Production costs and markups

To support households and businesses during the pandemic, the Federal Reserve lowered the federal funds rate target to essentially zero, and the federal government provided large fiscal transfers and increased unemployment benefits. These policies boosted demand for goods and services, especially as the economy recovered from the depth of the pandemic.

The increase in overall demand, combined with supply shortages, boosted the costs of production, contributing to the surge in inflation during the post-pandemic recovery. Although labor costs account for a large part of firms’ total production costs, real labor costs were falling between early 2021 and mid-2022 such that the increases in prices outpaced those in nominal wages. This makes it unlikely that labor costs were driving the surge in inflation.

Instead, we focus on another potential alternative driver of inflation that resulted from firms’ ability to adjust prices, known as pricing power. As demand for goods surged early in the post-pandemic recovery, companies may have had a greater ability to raise their prices above their production costs, a gap known as markups. Following a sharp drop in spending at the height of the pandemic, people may have become eager to resume normal spending patterns and hence more tolerant to price increases than in the past. In fact, growth of nonfinancial corporate profits accelerated in the early part of the recovery (see Figure 1), suggesting that companies had increased pricing power. Some studies have pointed to the strong growth in nonfinancial corporate profits in 2021 as evidence that increased markups have contributed to inflation (see, for example, Weber and Wasmer 2023). However, the figure also shows that growth in corporate profits is typically volatile. Corporate profits tend to rise in the early stages of economic recoveries. Data for the current recovery show that the increase in corporate profits is not particularly pronounced compared with previous recoveries.

Figure 1 Profit growth for nonfinancial businesses

More importantly, corporate profits are an imperfect measure of a firm’s pricing power because several other factors can drive changes in profitability. For instance, much of the recent rise in corporate profits can be attributed to lower business taxes and higher subsidies from pandemic-related government support, as well as lower net interest payments due to monetary policy accommodation (Pallazzo 2023).

Instead of relying on profits as a measure of pricing power, we construct direct measures of markups based on standard economic models. Theory suggests that companies set prices as a markup over variable production costs, and that markup can be inferred from the share of a firm’s revenue spent on a given variable production factor, such as labor or intermediate goods. Over the period of data we use, we assume that the specific proportion of a company’s production costs going toward inputs does not change. If the share of a firm’s revenue used for inputs falls, it would imply a rise in the firm’s price-cost margin or markup. In our main analysis, we use industry-level data from the Bureau of Economic Analysis (BEA) to compute markups based on the share of revenue spent on intermediate inputs. Our results are similar if we instead use the share of revenue going toward labor costs.

We compare the evolution of markups to that of prices, as measured by the PCE price index, since the recovery from the pandemic. In constructing this price index, the BEA takes into account changes in product characteristics (for instance, size) that could otherwise bias the inflation measure by comparing the prices of inherently different products over time. Similarly, based upon standard economic theory, our markup measure implicitly captures changes in those characteristics (see, for example, Aghion et al. 2023).

The post-pandemic evolution of markups

We examine the evolution of markups in each industry since the third quarter of 2020, the start of the post-pandemic recovery. Figure 2 shows that some sectors, such as the motor vehicles and petroleum industries, experienced large cumulative increases in markups during the recovery. Markups also rose substantially in general merchandise, such as department stores, and for other services, such as repair and maintenance, personal care, and laundry services. Since the start of the expansion, markups in those industries rose by over 10%—comparable in size to the cumulative increases over the same period in the core PCE price index, which excludes volatile food and energy components. However, the surge in inflation through June 2022 was broad based, with prices also rising substantially outside of these sectors. Thus, understanding the importance of markups for driving inflation requires a macroeconomic perspective that examines the evolution of aggregate markups across all sectors of the economy.

Figure 2 Cumulative changes in markups for salient industries

The role of aggregate markups in the economy

To assess how much markup changes contribute to movements in inflation more broadly, we use our industry-level measurements to calculate an aggregate markup at the macroeconomic level. We aggregate the cumulative changes in industry markups, applying two different weighting methods, as displayed in Figure 3. In the first method (green line), we match our industry categories to the spending categories in the core PCE price index for ease of comparison; we then use the PCE weights for each category to compute the aggregate markup. Alternatively, we use each industry’s cost weights to compute the aggregate markup (blue line). Regardless of the weighting method, Figure 3 shows that aggregate markups have stayed essentially flat since the start of the recovery, while the core PCE price index (gray line) rose by more than 10%. Thus, changes in markups are not likely to be the main driver of inflation during the recovery, which aligns with results from Glover, Mustre-del-Río, and von Ende-Becker (2023) and Hornstein (2023) using different methodologies or data. Markups also have not played much of a role in the slowing of inflation since the summer of 2022.

Figure 3 Cumulative changes in aggregate markups and prices

Moreover, the path of aggregate markups over the past three years is not unusual compared with previous recoveries. Figure 4 shows the cumulative changes in aggregate markups since the start of the current recovery (dark blue line), alongside aggregate markups following the 1991 (green line), 2001 (yellow line), and 2008 (light blue line) recessions. Aggregate markups have stayed roughly constant throughout all four recoveries.

Figure 4 Cumulative changes of aggregate markups in recoveries

Firms’ pricing power may change over time, resulting in markup fluctuations. In this Letter , we examine whether increases in markups played an important role during the inflation surge between early 2021 and mid-2022 and if declines in markups have contributed to disinflation since then. Using industry-level data, we show that markups did rise substantially in a few important sectors, such as motor vehicles and petroleum products. However, aggregate markups—the more relevant measure for overall inflation—have stayed essentially flat since the start of the recovery. As such, rising markups have not been a main driver of the recent surge and subsequent decline in inflation during the current recovery.

Aghion, Philippe, Antonin Bergeaud, Timo Boppart, Peter J. Klenow, and Huiyu Li. 2023. “A Theory of Falling Growth and Rising Rents.”  Review of Economic Studies  90(6), pp.2,675-2,702.

Glover, Andrew, José Mustre-del-Río, and Alice von Ende-Becker. 2023. “ How Much Have Record Corporate Profits Contributed to Recent Inflation? ” FRB Kansas City Economic Review 108(1).

Hornstein, Andreas. 2023. “ Profits and Inflation in the Time of Covid .” FRB Richmond Economic Brief 23-38 (November).

Liu, Zheng, and Thuy Lan Nguyen. 2023. “ Global Supply Chain Pressures and U.S. Inflation .” FRBSF Economic Letter 2023-14 (June 20).

Palazzo, Berardino. 2023. “ Corporate Profits in the Aftermath of COVID-19 .” FEDS Notes , Federal Reserve Board of Governors, September 8.

Weber, Isabella M. and Evan Wasner. 2023. “Sellers’ Inflation, Profits and Conflict: Why Can Large Firms Hike Prices in an Emergency?” Review of Keynesian Economics 11(2), pp. 183-213.

Opinions expressed in FRBSF Economic Letter do not necessarily reflect the views of the management of the Federal Reserve Bank of San Francisco or of the Board of Governors of the Federal Reserve System. This publication is edited by Anita Todd and Karen Barnes. Permission to reprint portions of articles or whole articles must be obtained in writing. Please send editorial comments and requests for reprint permission to [email protected]