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 polychaetes, comparatively few ecological studies have been carried out in shallow waters (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 structure. The aim of this study is to investigate the structure of the polychaete assemblages in a shallow soft bottom environment in the Antarctic and to assess the relationships with bottom type and ice effects. The samples were taken in December 1994 along a transect comprising four sampling stations ranging from 6-25 m depth, adjacent to the Brazilian Antarctic Station "Comandante Ferraz" at Martel Inlet, Admiralty Bay. Two additional stations were established at a depth of 18 m in order to study the effect of ice-scouring. Five replicates per station were sampled with corers taken by SCUBA divers. The polychaete distribution showed a distinct zonation pattern as a function of depth induced mainly by sedimentary differences and ice-scouring. The polychaete density, biomass and species diversity increased with depth. 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: Apistobranchus gudrunae, Tharyx cf. cincinnatus, Leitoscoloplos kerguelensis and Ophryotrocha 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 more abundant at the shallow stations.