The Subtidal seaweed communities of Bare Island, Botany Bay

Most descriptive studies on Australian algal ecology have been concerned with the intertidal region of rocky shores (Womersley, 1981a). Indeed, the early work of Dakin et al. (1984) on New South Wales shores, and Womersley’s studies on Kangaroo Island, placed Australian studies well to the fore internationally. Since the 1950’s, descriptive accounts have been published for much of the rest of the Australian coastline, but until SCUBA techniques became widely adopted, there were only brief accounts of subtidal algae, and these were based on observations on the immediate Subtidal zone. The work of Shepherd and Womersley (1970, 1971, 1976) in southern Australia has resulted in a descriptive framework for subtidal zonation on wave exposed rocky shores. The sublittoral communities can be fitted into a number of descriptive categories, and these are qualitatively distinct enough to be recognised as three zones (Womersley, 1981a). They are: an upper sublittoral zone, characterized by a short red-algal turf; a mid sublittoral zone, dominated by large brown algae or ‘kelps’; and a lower sublittoral zone with delicate and diverse red algae. The extent and distinctiveness of each zone depends on the degree of water motion, and the degree of attenuation of light intensity with depth.