Polychaete distribution in the near-shore zone of Martel Inlet, Admiralty Bay (King George Island, Antarctica)

Although a considerable amount of literature exists on Antarctic polychaete s, comparatively few ecological studies have been carried out in shallow wa ters (to 30 m). In these environments, inherent factors such as freezing of the intertidal and upper sublittoral zones, iceberg scouring and formation of anchor ice greatly influence the faunal distribution and community stru cture. The aim of this study is to investigate the structure of the polycha ete assemblages in a shallow soft bottom environment in the Antarctic and t o assess the relationships with bottom type and ice effects. The samples we re taken in December 1994 along a transect comprising four sampling station s ranging from 6-25 m depth, adjacent to the Brazilian Antarctic Station "C omandante Ferraz" at Martel Inlet, Admiralty Bay. Two additional stations w ere established at a depth of 18 m in order to study the effect of ice-scou ring. Five replicates per station were sampled with corers taken by SCUBA d ivers. The polychaete distribution showed a distinct zonation pattern as a function of depth induced mainly by sedimentary differences and ice-scourin g. The polychaete density, biomass and species diversity increased with dep th. In the area affected by ice-scouring, these structural parameters were more variable. A total of 31 species in 18 families was recorded across the sampling area. Four species accounted for 80% of the total abundance: Apis tobranchus gudrunae, Tharyx cincinnatus, Leitoscoloplos kerguelensis and Op hryotrocha notialis. Certain tube-dwelling polychaetes, such as Leaena cf. collaris and Asychis amphiglypta, occurred only at the 18 and 25 m stations where the ice-effects are less than at the shallower stations. Conversely, some species, notably those belonging to taxa known to be opportunistic in life-style, such as Ophryotrocha notialis and Microspio cf moorei, were mo re abundant at the shallow stations.