Particle Fluxes and Sédiment Characteristics at Three
Selected Sites in the Ross Sea (Antarctica)
M. Ravaioli1, M. Frignani1, M.C. Gambi2, L. Labbrozzi1 and L. Langone1
’lstituto di Geologia Marina, CNR, Via Gobetti 101, Bologna, Italy
2Stazione Zoologica “A. Dohrn”, Laboratory of Benthic Ecology, Napoli, Italy
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 sédiments were described and analysed for macrobenthos composition and concentrations of biogenic components. The three
sites show different lithologies: A and B are subject to présent open-sea biogenic sédimentation and differ only slightly, whereas C, being winnowed by
strong bottom currents, is characterised by a residual glacial-marine sédiment.
210Pbex inventories suggest that both sites A and B are subject to processes of
focusing, thus collecting sédiments transported from nearby areas. Apparent
burial rates were calculated on the basis of 210Pb chronologies and, for core B,
corrected using 14C 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 210Pbex profiles: using 14C dates a factor of 2.7 was calculated for site B.
Benthic communities differ in composition, density and structure. The présence 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 sédiment instability. These différences 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.
1 Introduction
Sédiments of the Southern Océan, and those of the Ross Sea in particular, accumulate high amounts of biogenic silica. Ledford-Hoffman et al. [ 1 ], on the basis of
210Pbex chronologies, estimated that as much as a quarter of the dissolved silica
supplied to the world océans by rivers and hydrothermal vents may be accumulating in the deposits of the Antarctic continental shelf. DeMaster et al. [2, 3]
established, using 14C-derived accumulation rates, that the total flux of biogenic
silica to the Ross Sea sédiments is approximately an order one magnitude lower
than the previous estimâtes. In practice, the extent of biogenic sédimentation, its
Selected Sites in the Ross Sea (Antarctica)
M. Ravaioli1, M. Frignani1, M.C. Gambi2, L. Labbrozzi1 and L. Langone1
’lstituto di Geologia Marina, CNR, Via Gobetti 101, Bologna, Italy
2Stazione Zoologica “A. Dohrn”, Laboratory of Benthic Ecology, Napoli, Italy
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 sédiments were described and analysed for macrobenthos composition and concentrations of biogenic components. The three
sites show different lithologies: A and B are subject to présent open-sea biogenic sédimentation and differ only slightly, whereas C, being winnowed by
strong bottom currents, is characterised by a residual glacial-marine sédiment.
210Pbex inventories suggest that both sites A and B are subject to processes of
focusing, thus collecting sédiments transported from nearby areas. Apparent
burial rates were calculated on the basis of 210Pb chronologies and, for core B,
corrected using 14C 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 210Pbex profiles: using 14C dates a factor of 2.7 was calculated for site B.
Benthic communities differ in composition, density and structure. The présence 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 sédiment instability. These différences 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.
1 Introduction
Sédiments of the Southern Océan, and those of the Ross Sea in particular, accumulate high amounts of biogenic silica. Ledford-Hoffman et al. [ 1 ], on the basis of
210Pbex chronologies, estimated that as much as a quarter of the dissolved silica
supplied to the world océans by rivers and hydrothermal vents may be accumulating in the deposits of the Antarctic continental shelf. DeMaster et al. [2, 3]
established, using 14C-derived accumulation rates, that the total flux of biogenic
silica to the Ross Sea sédiments is approximately an order one magnitude lower
than the previous estimâtes. In practice, the extent of biogenic sédimentation, its