Seasonal and interannual variability of feeding in Antarctic benthos

The seasonal and interannual variability of feeding in 15 species of benthic marine suspension feeder was studied over 8 yr at Ryder Bay, Antarctica. Feeding was strongly seasonal in bryozoans, gorgonians, polychaetes, and dendrochirote holothurians. The winter non-feeding period was longest in the holothurians and shortest in bryozoans. Bryozoans started feeding in late winter at very low chlorophyll concentrations, often when surface fast-ice was still present. In hydroids and actinians, feeding tentacles were deployed continuously throughout the year, though hydroid feeding intensity declined slightly in late winter. Water column phytoplankton biomass was strongly seasonal with marked interannual variability in the timing and intensity of the bloom, driven principally by ice dynamics. Correlation across years between the start of feeding and the development of the bloom was poor, and in seasons when a dense spring bloom of benthic filamentous microalgae developed, the start of feeding in many benthic species was delayed. This study indicates that feeding in benthic marine suspension feeders in Antarctica is influenced by factors additional to the seasonal availability of food in the water column.