Composition of Subtidal Macroalgal Communities of the Lower Gulf Waters of South Australia, with Reference to Water Movement and Geographical Separation

Abstract

Differences exist in the floristic composition of the canopy of macroalgal communities in the partially protected waters of sites on the Yorke and Fleurieu peninsulas, South Australia. These differences were quantified and related to the effects of wave force and geographical separation. The canopies of the communities were dominated by species of Cystophora J.Agardh and/or Sargassum C.Agardh and the biomass ratio of these genera was found to be highly correlated with wave force. Diversity was maximal at sites of intermediate exposure, whereas total biomass increased with the wave energy of the site. The common occurrence of some species at a number of sites supports the proposition that these sites occur within a single biogeographic province. The composition of these protected gulf communities is consistent with the trends previously demonstrated for exposed oceanic sites of the same region.