The role of disturbance in maintaining diversity of benthic macroalgal assemblages in southwestern Australia
Japanese Society of Phycology
Faculty of Computing, Health and Science
Health and Science Faculty Office/ Centre for Marine Ecosystems Research
Temperate Western Australia (WA) is home with one of the most speciose macroalgal assemblages in the world. Species diversity in WA subtidal macroalgal assemblages is first described along 100 km of temperate coastline between Cape Leeuwin and Cape Naturaliste, southwestern Australia. A large amount of variation in the macroalgal assemblage was significantly related to whether the substratum was limestone or granite, depth was m, and whether the reef was high relief (>2 m), or low relief. Combined with the habitat driven differences in assemblage structure, macroalgal assemblages were also influenced by the presence of a canopy of Ecklonia radiata (C. Agardh) J. Agardh: species richness was reduced and assemblage composition altered under canopies of this kelp. A clearance experiment, to test whether changes in macroalgal assemblages were related to the presence of E. radiata, was performed at Hamelin Bay. Species richness in cleared treatments was double that under E. radiata canopy and there was a significant shift in assemblage composition towards a more speciose Sargassum spp. dominated assemblage. Ecklonia radiata canopy was shown to have a negative influence on species richness and assemblage structure of macroalgae in temperate southwestern Australia. Gap creation in E. radiate kelp beds resulted in high species diversity and smallscale species turnover. The contemporary process of physical disturbance and the subsequent gap creation in E. radiate beds is an important process in maintenance of contemporary diversity of marine macroalgae in temperate Western Australia.