Ecological significance and commercial harvesting of drifting and beach-cast macro-algae and seagrasses in Australia: a review

Abstract

This review provides an overview of aspects of the ecology of drifting and beach-cast macroalgae and marine angiosperms in respect to present and potential commercial use of that resource in Australia. It sets the scene with sections on industries that utilise macro-algae and seagrasses, the ecology of littoral and nearshore sublittoral ecosystems and the processes of deposition of beach-cast macro-algae and seagrasses on beaches. It then describes the major economic macro-algae and seagrasses that occur as beach-cast wrack, with an emphasis on known information on habitat distribution, geographical range, and harvesting issues. Gaps in scientific knowledge are pointed out. The priority areas of future research were found to be: • The importance of beach accumulations of macro-algae and seagrasses on feeding and nesting shorebirds; • Whether available resource allows for ecologically and economically sustainable harvesting; • A survey of present and potential commercial macro-algae and seagrasses: studying biomass, density and annual production rates, interannual variability of recruitment into living stands, the effect of harvesting on trophodynamics and community structure and the stability of the resource base for economically sustainable harvesting; • An assessment of the importance of wrack in recycling nutrients and detritus to nearshore coastal ecosystems at wider geographical scales than previous work. This research should assess the dependence of offshore production on nutrients and detritus that are broken down in beachwracks.