Filtration activity of invasive mussel species under wave disturbance conditions

Abstract

Self-purification is one of the most important ecosystem functions of rivers. Multiple human activities regularly impact this ecosystem service, consequently altering river morphology, hydrology, and the composition of biotic assemblages that contribute to self-purification. However, little quantitative information is available about the importance of such impacts. Hence, we tested how invasive mussel species contribute to self-purification under disturbed riverine conditions. In laboratory experiments, invasive mussel species equipped with magnetic sensors that recorded filtration activity were exposed to artificial waves of varying intensity that simulated the hydraulic effects of inland navigation. Our results suggest that invasive mussel species are more resistant to wave disturbance compared to native species, as estimated threshold values for initiating shell closure are very high (Dreissena rostriformis bugensis) or the duration (Corbicula fluminea) and degree of shell closing (D. rostriformis bugensis, C. fluminea) very low. Also we demonstrated that the invasive species D. rostriformis bugensis and C. fluminea continued filtering during wave impact, whereas Dreissena polymorpha did not behave significantly differently than previously studied native mussel species, based on the studied susceptibility parameters. Thus, D. rostriformis bugensis and C. fluminea appear to be pre-adapted to hydraulic or morphological disturbance, and may compensate against other losses regarding this important ecosystem function in rivers that are intensively used for inland navigation. However, as the dominance of invasive species in river systems may disrupt natural food webs, this compensation of filter-feeding activity may be accompanied by the loss of other ecosystem functions.