James Cotner
Professor
Ecology, Evolution, and Behavior
Microbial metabolism has changed the composition of the Earth, including the atmosphere, lakes and oceans over nearly four billion years of life on the planet. We examine how microbes affect aquatic environments, primarily freshwater, via their composition, metabolism and production of greenhouse gases such as carbon dioxide and methane. Our work uses ecological stoichiometry as a framework to help us understand the dynamics of microbes and the biogeochemical cycles of important elements such as carbon, nitrogen and phosphorus in lakes, ponds and streams.
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Research statement
I seek to understand the role of heterotrophic bacteria in regulating production versus decomposition in aquatic environments.
Because most organic carbon burial occurs in aquatic ecosystems, they are critical to carbon dynamics on Earth. Furthermore, because heterotrophic bacteria are the most numerous organisms on the planet, they play a critical role in carbon fluxes in lakes and the ocean. Most carbon passes through "the microbial loop" on the way to its ultimate fate, either as storage in sediments or respiration as carbon dioxide. The availability of inorganic nutrients, especially phosphorus (P), plays an important role in the regulation of carbon fluxes in aquatic ecosystems through its impact on bacteria. In the coastal ocean and eutrophic lakes (high P availability), relatively low quantities of primary production funnels through bacteria and the microbial loop, increasing nutrient and carbon availability to the remainder of the food web. This contrasts with most of the ocean and many oligotrophic (low P availability) lakes where bacteria, because of their high affinity for P, are the main biomass component and the most metabolically active part of the microbial loop. Consequently, if you would like to catch fish, you probably would not want to spend most of your time in the oligotrophic gyres of the open ocean or the middle of Lake Superior. Because of their critical metabolic function in the biosphere, bacteria have significant impacts on the geochemistry of soils, lakes, rivers and oceans, including cycling and food web dynamics of contaminants, such as mercury and PCB's.
I have examined microbial processes in a wide variety of habitats; pelagic and benthic, freshwater and marine, lotic and lentic, and natural and human-impacted systems. I am particularly interested in the impacts of humans on microbial functions in ecosystems and global biogeochemical processes.
Education
Ph.D., University of Michigan, Ann Arbor, 1990