SUBLITTORAL EPIFAUNAL COMMUNITIES AT SIGNY ISLAND, ANTARCTICA .2. BELOW THE ICE-FOOT ZONE

Photographic samples were taken every 5 m along two 40 m transects on mostly rock face at Signy Island, Antarctica, during the austral winte r of 1991. Dense and taxonomically rich communities of benthos occurre d at most of the sublittoral study locations. These communities, howev er, varied significantly with substratum type, substratum profile and depth. Algae were generally the largest occupiers of space, but the ar ea of substratum colonised by animal taxa increased whenever the profi le approached vertical. Shallower than 15 m, disturbance effects, larg ely from ice, restricted community development to a high degree, but t he frequency of disturbance at 25 m appeared to maintain high diversit y by preventing domination of the assemblage by a few competitively su perior taxa. Bryozoans, and to a lesser extent sponges, were the most abundant animal phyla. Among the bryozoans, species with an encrusting growth form occurred at the shallowest depths followed by encrusting massive/foliaceous species and, at 40 m, the erect flexible forms. The ratio of encrusting to erect bryozoan species changed rapidly over th e 0 to 50 m depth zone, from exclusively encrusting at 0 to 5 m to app roaching 1 at 50 m. The erect bryozoans studied, from the shallow subl ittoral to 290 m, could be classified as encrusting massive (foliaceou s), erect flexible or erect rigid forms. There was some suggestion, de spite the overlap between groups and considerable intra-group variatio n, that encrusting massive forms were abundant in the shallowest water , followed by erect flexible forms and then erect rigid forms with inc reasing depth. Some species which occurred as encrusting massive/folia ceous forms in deeper water occurred mostly in encrusting form only in shallow water (<15 m).