Flow, flux and feeding in freshwater mussels

Unionid mussels are important constituents of aquatic systems that are affected by anthropogenic changes in hydrology and concomitant increases in suspended solids, yet little is known about the effects of flow on their suspension feeding. We examined the clearance rates (CR) of four species of freshwater mussels (Lampsilis siliquoidea, Lampsilis fasciola, Ligumia nasuta and Villosa iris) to determine whether they feed selectively on river seston and how this may vary with algal flux (concentration × velocity). The CR for the Lampsilis species was also determined using seston particle size, particle fluorescence, and algal taxon. The CR of all species increased linearly with flow chamber velocity, but exhibited saturation-like kinetics with increasing algal flux. The CR of Lampsilis species were higher for larger (>10 um) vs. smaller (<10 um) particles, the latter of which were numerically dominant in river seston. The CR of Lampsilis mussels on most of the algal taxa declined (li...