Algal flux affects the clearance rates of recently metamorphosed freshwater mussels

Abstract

Despite their role as ecosystem engineers, which is in large part a consequence of their suspension feeding activities, the early life history of unionid mussels is not well understood. We examined the suspension feeding rates (i.e., clearance rates, CR) of recently metamorphosed juvenile Lampsilis siliquoidea (1–4 week old), Lampsilis fasciola (1–3 week old), Villosa iris (2 week old), and Ligumia nasuta (1 week old) under ecologically relevant flux conditions in a recirculating racetrack flow chamber system. The range of velocities examined was determined experimentally using a permeameter containing riverbed material (63 μm to 6.5 cm diameter) in which juvenile mussels are thought to reside. The CR of the juvenile unionid species increased linearly with algal flux and the ranking of CR among species was V. iris > L. siliquoidea > L. nasuta > L. fasciola. CR also increased with the age (or size) of the mussel cohort but within a species CR increased non-linearly with shell length of the individual. These results provide new insight into the feeding abilities of recently metamorphosed juvenile mussels as well as potential threats to their growth and survival, which contributes to our understanding of their habitat requirements and may assist in the conservation of this imperiled taxon.