Description:
<p>This paper examines changes in species richness, abundance, and biomass of the intertidal benthic macrofauna of wave exposed sandy beaches in response to changes in beach type from reflective to dissipative extremes. Trends in six different geographical areas are compared, making use of both published data and recent field data from the south central coast of Chile. A new index, based on the log of the dimensionless fall velocity, which incorporates measures of wave energy, sand fall velocity, and tidal range, provides a better estimate of beach type than the dimensionless fall velocity alone. Species richness is found to be controlled primarily by the physical environment, increasing predictably from reflective to dissipative beaches. This control appears to be a conservative feature of sandy beaches, differing little between different zoogeographic provinces. Abundance and biomass follow similar patterns but are more variable and appear related also to surf zone productivity and wrack inputs, which in turn are influenced by wave energy. Although sand particle size and wave climate are both important, we argue that direct control on beach populations is via the swash climate, which changes significantly between different beach types. Morphology, body size, means of locomotion, and taxonomic composition of the fauna may demonstrate evolutionary consequences of adaptation to different swash climates.</p>