Phytodetritus deposited on the Antarctic shelf and upper slope: its relevance for the benthic system

Underwater photography was used to ascertain regional, seasonal, interannual or depth dependent variations in the occurrence of phytodetritus on the Antarctic seafloor in order to explain the patchy distribution patterns of the benthos. The information was obtained from an average of 63 photographs taken at each of 76 stations in the Weddell and Lazarev Sea along a 2300 km coastline during four austral summers between 1986 and 1991. In areas where the shelf was broader than 80 km, the sediment showed a significantly higher phytodetritus cover than on the narrower shelf. This can probably be explained by the lower current velocity on the broader shelf. Significantly higher percentages of phytodetritus cover were also found on the seafloor in areas where the megabenthos cover was relatively low. These results indicate that in areas with a low current velocity, organic particles sink relatively fast onto the seafloor where they are available mainly for deposit feeders. The generally more abundant filter feeders are better adapted to a higher current velocity which transports the particles mainly horizontally over longer periods. No significant relationships were found between other physical parameters and the occurrence of phytodetritus. Therefore, the results are also discussed under the aspect of a weak pelagic–benthic coupling, effected by the long-term development of the benthic system.