Subtidal Macrocalgal Assemblages in Temperate Australian Coastal Waters.

Bioregionalization and macroalgal assemblages are considered for temperate Australian CONCOM regions. These are eight regions which were proposed at the Second Council of Nature Conservation Ministers Technical Workshop (February 1985), in cooperation with the Bureau of Flora and Fauna (IUCN 1986). Ordination and cluster analyses of species complement of the different regions is consistent with the traditional biogeographic splitting of the temperate Australian coast into the Flindersian (transitional warm–cold temperate) along the southern Australian coast, and the south-east Maugean sub-province (cold temperate). The west Australian coast shows a gradual transition from the south to the subtropical flora of the Abrolhos Islands, while a Peronian Province is supported on the east coast. The analysis does not strongly support the Victorian and part of the South Australian coast as part of the Maugean. While visually conspicuous algae such as Durvillaea potatorum and Phyllospora comosa indicate that this region is closely aligned with the Tasmanian in the Maugean sub-province, when all species are taken into consideration, their contribution appears limited. Lord Howe Island is shown to have a rich and unique flora compared to the Australian mainland. In terms of macroalgal assemblages, distribution records for the larger, visually prominent algae are the most reliable and the review concentrates on these. Sargassum spp., Caulerpa spp. and Ecklonia radiata are conspicuous algae throughout temperate Australia. Cystophora spp. and Acrocarpia spp. are common along the southern coastline. Durvillaea potatorum and Phyllospora comosa dominate in the upper sublittoral from the west South Australian coast through to southern New South Wales including Tasmania. Macrocystis angustifolia is conspicuous in Victoria and northern Tasmania. In south-eastern Tasmania, Xiphophora gladiata, Caulocystis cephalornithos and Lessonia corrugata are common in shallower waters and Macrocystis pyrifera is prevalent in mid-water depths. The areal extent of assemblages are presently of being determined for South Australia, Western Australia and Port Phillip Bay. Regular mapping of the areal extent of macroalgal beds and monitoring changes would give a good indication of the state of the marine environment. Significant problem areas of large algal biomass blooms have been reported in the Peel–Harvey Estuary, and Princess Royal and Oyster harbours in Western Australia. Minor blooms are reported regularly in all States. ‘Blooms’ of algae as epiphytes on seagrasses have caused die-back of seagrasses in all States. Monitoring of frequency, severity and type of macroalgal bloom may indicate trends in environmental quality. There are number of macroalgal species believed to have been introduced to Australian waters. Two of the more significant are Undaria pinnatifida in Tasmania and Caulerpa filiformis on the New South Wales coast. Both blanket the rocky reef bottom for large areas, limiting colonisation by native algae. The first published record of a macroalgal extinction, that of Vanvoorstia bennettiana is believed to have been recorded at Botany Bay