In observance of World Water Day, _Nature Microbiology_ calls attention to research avenues that run through freshwater microbiology. World Water Day, a United Nations Observance, takes

place on 22 March and calls attention to the myriad roles fresh water plays in life on Earth. The observance is in line with Sustainable Development Goal 6, which has sights set on attaining

clean water and adequate sanitation for all. For many, access to safe, clean water makes it easy to take this resource for granted, but climate change, international conflict, natural

disasters and issues related to infrastructure, development and agriculture can all cause water scarcity and pollution. It is estimated that more than two billion people around the globe do

change. This year’s theme, Leveraging Water for Peace, comes on the heels of a year during which international conflicts multiplied and climate-related issues, such as droughts, flooding and

wildfires, were frequent occurrences. Water is an essential resource for life, and Leveraging Water for Peace highlights both how threats to access can compound or create new conflicts, and

how ensuring safety, equity and cooperation around water availability can yield far-reaching positive impacts. Safeguarding water resources in the near and long term will require action

from all sectors of research. At _Nature Microbiology_, our inclination is to wonder how the smallest biological entities on Earth intersect every facet of the water nexus. Threats to water

sanitation and pollution are often microbial in nature. Climate and land-use changes, as well as natural disasters, reshape freshwater systems with knock-on effects for the ecology1,2 and

transmission of bacterial, fungal, viral and parasitic pathogens, as well as for antimicrobial resistance. When it comes to attaining the objectives of Sustainable Development Goal 6,

microbes must be taken into consideration. In this Editorial, we briefly highlight broad umbrellas of emerging research in freshwater microbiology that should be considered if we are to

achieve these objectives. Natural disasters represent the most rapid mechanisms by which freshwater resources can be affected, but the subsequent impact on microbial dynamics is not

routinely considered. Flooding from severe storms as well as other natural disasters, such as earthquakes, that damage infrastructure rapidly alter the physical distribution of microbes and

can result in exposure to a suite of potentially pathogenic microbes either from the environment or through compromised wastewater treatment facilities3. In the aftermath of flood-related

disasters, fungi can colonize waterlogged buildings, leading to negative health implications after exposure3. Moving forward, investigations into how microbes impact the spread of

antimicrobial resistance genes and research into how microbial dynamics intersect with environmental and social justice efforts should be a focus. Even without a natural disaster, harmful

algal blooms in freshwater systems can also rapidly, and unpredictably, threaten public health. Lakes are essential drinking water resources, but persistent high temperatures and nutrient

runoff from land can trigger the proliferation of cyanobacteria that produce toxins that harm humans when consumed. As a result of these blooms, tap water can be rendered unsafe for millions

of people for weeks at a time4. Historical records, recent observations and modelling efforts all suggest that the frequency and duration of these harmful algal blooms will increase in the

future4,5. The conditions that favour harmful algal blooms could also pave the way for the increased abundance and activity of microbes that produce greenhouse gases such as methane and

nitrous oxide, and climate modelling studies suggest that emissions from inland waters are likely to increase under future climate conditions6. Open questions in freshwater microbial ecology

include a mechanistic understanding of how symbioses and interactions in these communities impact outcomes, for example interactions between methanogenic archaea that produce methane and

methanotrophs that consume methane, or more work into the role of phages and how they impact these dynamics7. Global climate and land-use changes that impact freshwater systems also

influence the spread of vector-borne diseases. The increased duration of warm and wet conditions, floods and deforestation all contribute to the increased spread of _Plasmodium_, the

causative agent of malaria, as well as viruses such as dengue, chikungunya and Zika, all of which are transmitted by mosquitoes that breed in water. Extreme weather events and human

disturbances can also impact the ecology of birds, which is exacerbating the spread of highly pathogenic avian influenza. These dynamics are discussed in two Comments in our recent focus

issue on microbes and climate change8,9. In addition to calling for the mitigation of climate and land-use changes, another theme that emerges from these pieces is the need for those in

power to take climate-related health impacts into account, to collaborate with microbiologists, to involve impacted communities in public-health discussions and to ensure that aid is

equitably distributed, especially to the most vulnerable populations. While the intersections of freshwater research and microbiology often take a negative slant, as a journal we believe

that impactful research paves the way for actionable solutions. At _Nature Microbiology_, we want to showcase the best research in all areas that touch on freshwater microbiology, with the

hope that it will fuel additional understanding and initiative. From basic research to policy and governmental decisions to international collaborations, we hope that increasing focus on

microbes and freshwater resources will hasten the realization of World Water Day’s goals. REFERENCES * Shabarova, T. et al. _Nat. Microbiol._ 6, 479–488 (2021). Article  CAS  PubMed  Google

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