Physiological energetics, growth and biomass allocation of mussels across the intertidal zone

High intertidal populations of suspension feeding bivalves exhibit reductions in potential feeding time that result from reduced periods of inundation. Determinations of growth and physiological performance of populations of mid- and high intertidal mussels (Guekensia demissa ) from salt marshes in South Carolina can be used to address this question. High intertidal mussels have considerably lesser somatic and reproductive biomass, but maintain similar proportional allocation of biomass to reproductive tissues than mussels from the mid-intertidal zone. Reduced periods of inundation have a stronger effect on growth of soft tissue than on shell growth. No consistent differences in feeding, absorption or metabolic rates were observed among mid- and high intertidal mussels, during periods of submergence or aerial exposure. Estimations of net energy balance from physiological measurements suggest the absence of physiological compensations for reduced feeding time by high intertidal mussels.