Microbial Ecology and Biogeochemistry in the Anthropocene Sea

There are a million microorganisms in a drop of water, but we have only a limited understanding of what these organisms do: what they ‘eat,’ how they survive, or how they interact.  However, we do know that the collective activities of these tiny cells drive global cycles of essential elements such as nitrogen, carbon, and oxygen.  As a result, microbial communities play a central role in controlling Earth’s climate and habitability—yet these global biogeochemical cycles have been subsequently altered by human activities.  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, and freshwater lakes in the Sierra Nevada.  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 agricultural runoff and phytoplankton blooms was featured on the front page of the Washington Post in December 2021.

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