Temporal and spatial variability in the community structure of the fauna of four sandy beaches in south-eastern New South Wales.

Abstract

Four intertidal sandy beaches with different exposures, La Perouse, Ocean Beach, Dolls Point, and Towra Point, were studied for temporal and spatial changes in faunal composition and community structure. Each of these beaches was sampled from 6 to 12 times between July 1980 and July 1981 using a 500 µm sieve. A stratified random sampling procedure across the intertidal zone isolated 40 660 individuals representing 85 species.

Distribution and abundance of species were strongly influenced by tidal level. Densities changed during the year but no seasonal changes in intertidal zonation patterns were found. Changes in density were correlated with the reproductive activities of the abundant species, especially Pseudolana concinna and Exoediceros maculosus at La Perouse, and Spio pacifica at Dolls Point and Towra Point. The number of species increased from high to low tide, and also increased with decreasing exposure to wave action. Crustaceans dominated the fauna in the most exposed site and decreased in abundance with increasing protection.

Ocean Beach experienced the least fluctuation in physical factors such as wave action, salinity, and temperature, and its fauna exhibited the highest diversity index (H') and evenness (J'), the most stable density, and the greatest stability in faunal composition through time. The highest densities and the most species were found at Towra Point, which also was the most protected site.