Ribbed mussel (Geukensia demissa) filtration services are driven by seasonal temperature and site-specific seston variability

Abstract

Ribbed mussels (Geukensia demissa) are ubiquitous intertidal invertebrates of eastern North American salt marshes, often living in close association with salt marsh cordgrass Spartina alterniflora. They are typically concentrated at the lower extent of the vegetated zone along tidal channels, but are also found across the marsh platform. As filter-feeding bivalves, ribbed mussels remove suspended micro-particulate matter and associated nutrients from the water column, potentially resulting in benefits to water quality. However, the magnitude of such ecosystem services may depend on temporal and spatial variation in the mussel's water clearance and particle filtration rates. The goal of this study was to identify sources of variation regarding the distribution of ribbed mussel filtration services.Seasonal-spring, summer, and fall- water clearance and particle filtration rates were quantified for ribbed mussels collected from three habitats- low marsh along main tidal channels; low marsh along intra-marsh creek networks; and from the high marsh- and replicated in four representative marshes- three in New Jersey and one in Rhode Island, USA, normalized by mussel dry tissue biomass. Clearance rates varied with seasonal temperatures, but exhibited low spatial variability among habitats and marshes, highlighting the importance of understanding the temporal physiological variability when calculating annual rates. In contrast, filtration rates were highly variable, driven largely by spatial variation in seston availability. Annual bulk filtration services provided by ribbed mussels are therefore largely driven by both temporal variability in water processing and spatial variations in food availability, and can therefore be predicted by integrating seasonal clearance rates and site-specific seston composition.