Benthic suspension feeders play an essential role in the trophic dynamics of near-shore waters. By efficiency removing planktonic cells and suspended particles from the water column, they contribute to benthic-pelagic coupling and to top-down control of planktonic communities . However, information regarding the in situ capture efficiency of different planktonic cells by common benthic suspension feeders is scarce. To narrow this gap we assessed the capture efficiency of different planktonic groups by four filter-feeding species common in Long Island Sound coastal communities: the blue mussel, Mytilus edulis ; the ribbed mussel, Geukensia demissa; the clubbed tunicate, Styela clava ; and the vase tunicate, Ciona intestinalis . Sampling was performed in situ during the summer and fall seasons, using the InEx-VacuSip method. This method allows in situ and continuous collection of paired inhaled and exhaled water from the animals. To examine patterns of prey particles captured by the animals , cell abundance in paired-water samples was analyzed by flow cytometry. Phytoplankton populations were grouped into cyanobacteria, large eukaryotes and small eukaryotic algae .
Both mussels and tunicates showed, in most cases, a higher capture efficiency for cyanobacteria compared to the larger “small eukaryotes” in situ. This finding could be the result of several physicochemical properties of the cyanobacteria, including possible aggregation of the cells. These potential mechanisms are currently being investigated.