Scaling Population Density to Body Size: Tests in Two Soft-Sediment Intertidal Communities

Abstract

An inverse relationship between population density and body size has been reported for a number of natural communities and taxonomic assemblages in terrestrial and aquatic systems. Such relationships have not been widely examined in marine communities. No evidence of an inverse relationship between population density and body size was found in samples of macrofauna from marine intertidal communities with soft sediments, exposed sand beaches and salt marsh tidal channels over a range of up to four orders of magnitude in population density and five orders of magnitude in body size. Relationships between population density and body size in those communities were generally not significant. For all but one of the samples, the slope of a linear regression between population density and body size was positive. We propose that the role of physical processes and disturbance in community structure, the nature of food and space resources, and the survival value conferred by size and hard exoskeletons contribute to that result for marine intertidal macrofauna communities in soft sediments.