Can benthivorous fish alter carbon dynamics in eutrophic reservoirs?


Thursday, March 8, 2012
Redfield Auditorium - 12:00 Noon
Dr. Amanda Spivak
Assistant Scientist, Marine Chemistry and Geochemistry, WHOI
co-sponsored event with CINAR

Freshwater ecosystems play an important role in the global carbon cycle. Watershed development coupled with high inputs of inorganic nutrients can lead to eutrophication and subsequent changes in carbon dynamics. For instance, recent mass balance analyses indicate that carbon burial is higher in eutrophic vs. oligotrophic systems and that eutrophic freshwater habitats may be globally significant carbon sinks. However, many studies overlook the role of animals in mediating carbon dynamics and burial in aquatic habitats. Feeding modes, such as detritivory, and foraging activities that cause sediment resuspension and bioturbation are widely recognized to affect sediment biogeochemistry and diagenesis. To investigate the importance of animal communities in freshwater ecosystems, we developed a model of carbon dynamics in a eutrophic reservoir with an abundant detritivorous fish, the gizzard shad (Dorosoma cepedianum). The model was calibrated with mass balance data of organic carbon sources and sinks. At present, the impoundment buries 693 – 861Mg OC y-1 and the model satisfactorily simulates this burial rate. The model predicts that a fifty percent population reduction or complete extinction would increase organic carbon burial by ~30% or ~40%, respectively. Overall, our findings indicate that the direct and indirect effects of benthivorous fish on carbon dynamics may be more important than previously thought.