Food availability and gut contents in the ascidian Cnemidocarpa verrucosa at Potter Cove, Antarctica

Abstract.

A high seasonality characterizes Antarctic environments, and generates marked differences in availability and composition of food for benthic filter feeders. During a year-round period at Potter Cove, Antarctica, algal pigment concentration (chlorophyll a) and organic matter were measured in water column and sediment samples. Chemical composition of gut contents of the ascidian Cnemidocarpa verrucosa was also analyzed. Despite the low standing stock, capture and absorption of organic matter were detected year-round, suggesting intake of other particles besides microalgae. The mechanism that provides food to the ascidians and epibenthic communities may be related to the supply of allochtonous particles, bottom resuspension events, and microbial community dynamics. Sea-ice cycles may affect food availability in terms of water-column mixing and benthic resuspension. The scarce primary production and the high amount of sedimented material are not limiting conditions in Potter Cove, which presents a rich ascidian community.