James B. Cotner
 Associate Professor, Dept. of Ecology, Evolution, and Behavior
Moos Chair in Limnology
Ph.D., University of Michigan, Ann Arbor, 1990
Contact Information
Phone: 612-625-1706
Fax: 612-624-6777
E-mail: cotne002@umn.edu
Graduate School Memberships
Ecology, Evolution, and Behavior; Quaternary Paleoecology; Water Resources Science.
Research Interests
Biological limnology and oceanography; Biogeochemistry; Microbial ecology.
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.
Selected Publications
Biddanda, B., M. Ogdahl, and J.B. Cotner. 2000. Contribution of heterotrophic bacteria to planktonic biomass and respiration in lakes and the ocean. Submitted to Limnology and Oceanography.
Cotner, J.B. 1999. Heterotrophic bacterial growth and nutrient limitation in large, oligotrophic lakes and oceans. Verh. Internat. Verein. Limnol. (In press)
Cotner, J.B., J.W. Ammerman, E.R. Peele, and E. Bentzen. 1997. Nutrient-limited bacterioplankton growth in the Sargasso Sea. Aquatic Microbial Ecology 13:141-149.
Cotner, J.B., W.S. Gardner, J.R. Johnson, R.H. Sada, J.F. Cavaletto, and R.T. Heath. 1995. Effects of zebra mussels (Dreissena polymorpha) on bacterioplankton: Evidence for both size-selective consumption and growth stimulation. Journal of Great Lakes Research 21:514-528.
Cotner, J.B., Jr. and W.S. Gardner. 1993. Heterotrophic bacterial mediation of ammonium and dissolved free amino acid fluxes in the Mississippi River plume. Marine Ecology Progress Series 93:75-87.
Cotner, J.B., Jr. and R.G. Wetzel. 1992. Uptake of dissolved inorganic and organic phosphorus compounds by phytoplankton and bacterioplankton. Limnology and Oceanography 37:232-243.
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