Microbial Ecology and Biogeochemistry in the Anthropocene Sea

There are a million microorganisms in a drop of water that range from well-known pathogens to organisms new to science.  These diverse microbial communities play a central role in controlling Earth’s climate and habitability, as the collective activities of these tiny cells drive global cycles of essential elements such as nitrogen, carbon, and oxygen.  However, human activities have subsequently disrupted global biogeochemical cycles in multiple ways, especially by altering Earth’s atmosphere and climate.  The overarching goal of our research is to connect these perspectives by developing a predictive understanding of microbial ecology and biogeochemistry in rapidly changing aquatic ecosystems.  We try to figure out: (1) what microbes can ‘do’ and how they do it; (2) how they interact with each other; (3) how this can change; and (4) what the implications are.

To achieve this, we use techniques ranging from stable isotope biogeochemistry to large ‘omic datasets generated via DNA and RNA sequencing.  We apply these to experimental manipulations and environmental gradients within the eastern tropical North Pacific ocean, ‘marine lakes’ in the islands of Palau, freshwater lakes in the Sierra Nevada, along the coast of California, and beyond. We seek to understand linkages and feedbacks among microbial communities and the biogeochemical processes that they mediate, and how these may be altered by (or resilient to) ocean deoxygenation, ocean acidification, pollution, and climate change.  For example, Mike’s early research on how agricultural runoff fuels phytoplankton blooms was featured on the front page of the Washington Post in December 2021.

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