Alternative food sources of native and non-native bivalves in a subtropical eutrophic lake

The aim of this study was to evaluate the consumption of alternative food sources (water column and sediment) and the potential competition under different conditions between Diplodon parallelopipedon (native) and Corbicula fluminea (non-native). We evaluated filtration and ingestion rates of water column at 6 and 24 h, held with and without organic matter and different phytoplankton types: needle-shaped green algae (Ankistrodesmus sp.) and filamentous cyanobacteria (Planktothrix agardhii) dominated communities. Our results confirmed higher filtration and ingestion rates per biomass unit for C. fluminea in the presence of sediment without organic matter. However, when we compared the filtration of bivalves held in sediment with organic matter, D. parallelopipedon rates were not significantly different from C. fluminea values. Moreover, in the presence of filamentous cyanobacteria, only C. fluminea filtration and ingestion rates decreased significantly. Our experimental results and previous field evidence concur that C. fluminea were not able to outcompete the native bivalves in organic matter rich sediment and cyanobacteria blooms conditions. The differential responses to the eutrophication process between exotic and native bivalves, apparently favoring the later, might buffer the potential competition interactions allowing their coexistence.