Marine macroalgae from the Gulf of Carpentaria, tropical northern Australia

Over the last two decades, CSIRO surveys of the seagrass communities in the south-western Gulf of Carpentaria and at Groote Eylandt, the Northern Territory, have provided opportunities for the collection of marine macroalgae from this poorly explored, remote region. Although the cruises did not concentrate on macroalgal communities which typically grow on rocky substrates, 64 specific and subspecific taxa of marine Chlorophyta, Phaeophyceae and Rhodophyta were collected, including 30 species newly recorded for the Gulf. The majority of Gulf species also occur on the tropical eastern Australian coast. One hundred and thirteen macroalgal taxa are now known to occur in the Gulf of Carpentaria, the number from the present study supplemented by collections from the 1948 Arnhem Land Expedition and from an ethnobiological study on Groote Eylandt during the 1970s. Twelve species are recorded by all three Gulf studies and 23 species are reported by two studies. The relatively low number of species common to more than one study is thought to result from each study's narrow sampling window which fails to adequately document the considerable spatial and temporal variability of macroalgal species. Accordingly, the number of species presently recorded for the Gulf is considered to be an underestimate of macroalgal biodiversity for the region. It is clear that further detailed taxonomic and ecological investigations are urgently required before the full extent of macroalgal biodiversity in tropical Australia can be appreciated.