Regulation of Heterotrophic Microbial Processes in Lake Ecosystems

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New York Botanical Garden, Institute of Ecosystem Studies Heterotrophic microorganisms are responsible for a major portion of the biological productivity and biogeochemical cycling in ecosystems. Regulation of microbial processes, however, is poorly understood. This project will examine how two key properties of aquatic ecosystems, primary production and food web structure, regulate the biomass, respiration, and productivity of heterotrophic microbes including bacteria, flagellated protozoans and ciliated protozoans. This research will take advantage of whole lake experiments already funded by NSF. Food webs in four lakes will be manipulated to enhance dominance by either planktivorous or piscivorous fish. Nutrient loading in two of these lakes with alternative food webs will be increased to elevate phytoplankton primary production and biomass. Pace and Cole hypothesize that heterotrophic microbial processes are a relatively conservative feature in aquatic ecosystems. Changes in heterotrophic microbial processes in these experiments will be primarily a result of changes in primary production and phytoplankton biomass and secondarily a result of changes in phytoplankton community structure. To strengthen the general applicability of the experimental results, these hypotheses will be tested by a comparative study of bacterial productivity and biomass in 20 lakes. Simulation and inverse food web models will be used to examine how variability in food web structure and primary production influences microbial processes and how variability in microbial processes influence other components of the system. Pace and Cole are productive young scientists. The institutional support for this research is excellent.