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SFS Annual Meeting

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Permafrost loss due to increasing temperature at high latitudes alters watershed flowpaths and is predicted to increase nutrient export to streams. Slight changes in water chemistry and energy supply can significantly impact stream food webs. Within biofilm communities, autotrophic and heterotrophic organisms compete for inorganic nutrients with the outcome dependent on temperature, light availability, and quality of dissolved organic matter. In the Caribou-Poker Creeks Research Watershed (AK, USA), sub-catchments are underlain with varying permafrost extents, creating an ideal location for quantifying the impacts of permafrost thaw and resulting variation in stream water chemistry on biofilm structure and function. Our objective was to determine how changes in light availability, inorganic nutrient concentration, and lability of dissolved organic matter influence competition between autotrophs and heterotrophs in stream biofilms. We predicted that with abundant light and labile dissolved organic matter, inorganic nutrient concentrations will dictate autotrophic primary production and heterotrophic respiration, as well as biomass, but with low light and recalcitrant dissolved organic matter, inorganic nutrients will become secondary controls. We used nutrient diffusing substrata and nutrient uptake experiments to explore the outcome of competition for nutrients within boreal forest headwater stream biofilms.

Sophie Weaver (Primary Presenter/Author), University of Alaska Fairbanks,;

Jeremy Jones (Co-Presenter/Co-Author), Univeristy of Alaska Fairbanks,;