Effects of physical state and latitude on sandy beach macrofauna of Eastern and Southern Australia

Macrofaunal communities of beaches in eastern Australia were investigated for relationships of species number, abundance, and biomass with the physical characteristics of the beach environment (expressed numerically as the dimensionless fall velocity and beach state index [BSI]). A range of physical beach states across three biogeographical regions was sampled for macrofauna at low tide during summer months, and the data were regressed and compared. Results showed that species number, abundance, and biomass increased from reflective to ultradissipative shore conditions (abundance and biomass increasing logarithmically). Species number showed the same numerical relationship with BSI for each of the regions studied, the common regression equation showing that nearly 90% of variation in macrofaunal species number between beaches can be explained by this compound index of physical parameters. Abundance and biomass showed similarities in response to BSI, although at different orders of magnitude by region. The results of a multiple regression including latitude suggest that, although species richness is almost directly related to physical beach processes, abundance and biomass are determined more by a combination of surf zone processes and climatic factors specific to each biogeographic region.