Dissolved Organic Matter Biogeochemistry: Linking Ecosystem Processes, Community Structure, and Microbial Dynamics in Streams.
Principal investigators:
Louis A. Kaplan, Stroud Research Center
David A. Stahl, University of Washington
Patrick G. Hatcher, Ohio State University
Robert H. Findlay, Miami University
Margaret Palmer, University of Maryland
Graduate student:
David Richardson, University of Maryland
This proposal asks (1) How cosmopolitan are the various species of bacteria?; (2) What determines if an organic molecule or compound is biodegradable? ; and (3) Can differences in bacterial community structure and dissolved organic matter (DOM) molecular structure be related to differences in function?
The nine study streams for this work lie within the Eastern Deciduous biome, the Southern Coniferous biome, and the Tropical Evergreen biome, providing contrasts and replication at the watershed scale. Our investigations will test working hypotheses: (1) Terrestrial plant species diversity generates high diversity in terrestrially-derived DOM and, in turn, increases diversity in the heterotrophic bacterial community, so that DOM diversity and bacterial diversity should increase from the Coniferous to the Deciduous, to the Tropical Evergreen forest; (2) Communities of heterotrophic bacteria are acclimated to the DOM from their own biome, and acclimation to DOM from another biome requires a replacement of genotypes rather than shifts in the abundance of existing genotypes or phenotypic adjustments; (3) Changes in the diversity of terrestrial sources of DOM associated with seasonality and disturbance within a single watershed alter the diversity of the heterotrophic community; and (4) Variance in the quantity of DOM influences bacterial biomass and production, while variance in the quality of DOM increases phenotypic and genotypic diversity within the bacterial community.
Our analytical approach to characterizing DOM and microbial communities involves measurements of concentration, composition, and structure. Collectively, these methods are sufficiently robust to allow us to pursue four research objectives: (1) Determine the diversity of DOM and the diversity of the heterotrophic bacterial community in different biomes; (2) Determine the abilities of bacteria from streams in different biomes to metabolize the DOM in streamwater from other streams within the same biome and from streams in other biomes (initially, upon short-term exposures, and upon long-term exposures); (3) Determine DOM diversity in streamwater and heterotrophic bacterial diversity and activity in different seasons and following storm disturbance within a single stream; and (4) Determine the biomass, production and diversity of bacterial communities exposed to either constant or variable DOM regimes.
This proposal will foster collaboration within the three disciplines of biogeochemistry, microbial ecology, and ecological theory and would benefit from the inclusion of a student with quantitative expertise.
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Overview