Particle Fluxes and Sediment Characteristics at Three Selected Sites in the Ross Sea (Antarctica)

Abstract

We studied three selected sites of the Ross Sea to understand the relationships between their depositional characteristics and benthic fauna. Box cores were collected at each site and sediments were described and analysed for macrobenthos composition and concentrations of biogenic components. The three sites show different lithologies: A and B are subject to present open-sea biogenic sedimentation and differ only slightly, whereas C, being winnowed by strong; bottom currents, is characterised by a residual glacial-marine sediment. Pb-210(ex) inventories suggest that both sites A and B are subject to processes of focusing, thus collecting sediments transported from nearby areas. Apparent burial rates were calculated on the basis of Pb-210 chronologies and, for core B, corrected using C-14 data. A and B show similar apparent mass accumulation rates (89 and 104 mg cm(-2) yr(-1), respectively) as well as burial rates of biogenic species. These rates are overestimated, due to the influence of deep mixing on the Pb-210(ex) profiles: using C-14 dates a factor of 2.7 was calculated for site B. Benthic communities differ in composition, density and structure. The presence of infaunal forms, mainly surface and sub-surface deposit feeders, with reworking capability characterise sites A and B, whereas at site C the community is mainly composed by epibenthic filter feeders and is strongly influenced by sediment instability. These differences are mainly due to bottom water dynamics and, when comparing a and B, to water depth and, perhaps, to the slightly different lithologies which reflect the locations of the sites and the different sources of sedimentary materials.