Introduced bivalves in freshwater ecosystems: the impact of Corbicula on organic matter dynamics in a sandy stream

Previous research on Corbicula fluminea (a well-established, non-native biv alve) has clearly shown that this single species impacts ecosystem processe s such as nutrient and dissolved organic carbon cycling in the water column of streams. Surprisingly, little was known about how Corbicula might influ ence similar processes in streambed sediments. Here, we used both laborator y and field experiments to determine how filter- and pedal-feeding by Corbi cula impact organic matter dynamics in the sandy streambed (Goose Creek, Vi rginia). Corbicula consumed significant quantities of organic material in t he streambed when conditions favored pedal-feeding but increased buried org anic matter stores when filter-feeding promoted deposition of organic matte r (by production of feces and pseudofeces). Corbicula contributed significa ntly to total benthic community respiration (and thus carbon dioxide produc tion), and used pedal-feeding on benthic organic material to grow at a fast er rate than that possible by filter-feeding alone. Corbicula should be an important coupler between benthic and pelagic processes because this bivalv e uses organic matter from both the water column and the stream sediments. Given the widespread occurrence of this species, we speculate that the intr oduction of Corbicula may have had major implications for organic matter dy namics in this and many other streams in the United States.