Spatial and Vertical Distribution of Benthic Littoral Communities in Terra Nova Bay

Abstract

The littoral benthic communities of the Ross Sea, except for McMurdo Sound, are poorly known. An analysis of the composition and distribution of the communities in Terra Nova Bay has been conducted down to the 150-m depth between Tethys Bay and Adelie Cove.These communities show a clear zonation according to depth and on the basis of some guide species. On hard bottoms, the upper zone down to the 2–3m depths, due to the presence of drifting pack ice, shows a very poor community, mainly composed by cyanobacteria and diatoms and the amphipod Paramoera walkeri. From 2–4m to 70m, the algal communities constitute welldefined belts. These algal belts represent shelter and a food source for diversified and abundant vagile fauna, among which the echinoid Sterechinus neumayeri and the asteroid Odontaster validus. From 70–120m, a complex community of sponges and anthozoans characterizes the rocks, reaching high values in biomass and species richness.Soft bottoms generally start at the 20–30m depth and are constituted by coarse sands and gravel where Alcyonium sp. is often found. Herein the communities are characterized by bivalves (Laternula elliptica, Yoldia eightsi, Adamussium colbecki) and polychaetes (Tharyx cincinnatus, Aglaophamus ornatus; Spiophanes tcherniai, Leitoscoloplos mawsoni). Much deeper, on muddy sands at about the 150-m depth, the polychaete Laonice weddellia characterizes the community, and brachiopods can be found on small gravel.