Distribution and abundance of giant sea anemones (Actiniaria) in subtropical eastern Australian waters

Abstract

Five of the 10 known Indo-Pacific giant anemone species were recorded on subtidal reefs within the eastern Australian subtropics (26°37′S to 30°56′S) during surveys between 1993 and 1995. Giant anemones had a patchy distribution among the 30 localities sampled, and species richness did not display any latitudinal trends within this province. Spatial distribution patterns and abundance of anemones were assessed from total counts and from line-intercept and belt transects. Anemone abundance was significantly higher on reefs to the leeward of the prevailing swell than on more exposed sites, at Julian Rocks and North Solitary Island, northern NSW. Significant reductions in anemone cover were detected among years within shallow reefal sites at North Solitary Island, coinciding with two major storm events. The abundance of the widespread Entacmaea quadricolor at North Solitary Island was the highest reported worldwide. Significant differences were detected between two morphological types of E. quadricolor in terms of microhabitat type, oral disk size and spatial distribution patterns. Important factors influencing the distribution, abundance and spatial patterns of giant anemones over both large and localized spatial scales appear to be water temperature, wave disturbance and water depth.