210
M. Ravaioli et al.
spatial variability as a function of primary production, bottom morphology and
water dynamics, and its relationship with living bottom fauna are aspects of the
Ross Sea ecology which are still relatively unknown.
The supply and préservation of organic matter, together with bottom sédiment
characteristics, may affect macrofaunal abundance and composition. Therefore
the water dynamics and burial rates of biogenic materials are key factors in determining the characteristics of the bottom environments. In recent years there has
been an increasing interest in the achievement of accurate sédiment chronologies
and mass accumulation rates for Antarctic continental margin deposits in order
to understand environmental processes, calculate fluxes and mass budgets for the
various sédiment components, and study paleoclimate records. Presently, radiocarbon dating is considered more reliable than 210Pbex data for establishing accurate rates of sédiment accumulation in the Ross Sea [2,3], but they can be better
used together to overcome the effect of mixing [4,5].
This research, carried out within the framework of the Italian Programma
Nazionale di Ricerche in Antartide, is aimed at understanding the characteristics
of three représentative sites of the Ross Sea with respect to biogenic fluxes, sédiment composition and macrobenthos populations.
2 Study Area
The study area and the sampling locations are shown in Fig. 1. Frignani et al. [6]
described the network of processes that détermine the formation, transport and
fate of the particulate matter and its rôle in the biogeochemical cycles in the Ross
Sea. The biogenic components formed in the surface layer, which are not dissolved
or recycled, sink via fecal pellets, cellular débris and aggregates [7] and accumulate
in sédiments of areas where water dynamics is weak. Smith and Nelson [8] suggested that algal blooms resuit from vertical stability imparted by melting ice that
begins in the polynya close to the Ross Ice Shelf, and expands northward. The patterns of surficial sédiments [9,10] and satellite imagery [11] suggest phytoplankton biomass and production gradients west to east and south to north. The three
study sites, located along the south to north direction of retreat of the marginal ice
zone, were chosen to study particle fluxes through the water column using moored
instruments (sédiment traps, current meters, transmissometers). Site A, located in
south-west Ross Sea at 810-m depth, is important to understand particle transport
and sédiment accumulation in proximity to the Ross Ice Shelf. The area is made
interesting by the initial phase of the ice margin retreat and Smith and Gordon
[12] found that phytoplankton production was dominated by the prymnesiophyte
Phaeocystis antarctica, although significant numbers of diatoms co-occurred.
Mooring A, operative since January 1994, is the subject of a co-operation with the
US program ROAVERRS. Site B, located in the center of the northern part of the
Joides Basin at 580-m depth, represents a setting characterised by high biosiliceous
sédiment accumulation. Mooring B was first deployed in December 1994. Finally,
site C, in the northern flank of the Mawson Bank very close to the shelf break, is
représentative of an environment with high energy and reworked sédiment.
Mooring C was left in place from December 1994 to January 1996.
M. Ravaioli et al.
spatial variability as a function of primary production, bottom morphology and
water dynamics, and its relationship with living bottom fauna are aspects of the
Ross Sea ecology which are still relatively unknown.
The supply and préservation of organic matter, together with bottom sédiment
characteristics, may affect macrofaunal abundance and composition. Therefore
the water dynamics and burial rates of biogenic materials are key factors in determining the characteristics of the bottom environments. In recent years there has
been an increasing interest in the achievement of accurate sédiment chronologies
and mass accumulation rates for Antarctic continental margin deposits in order
to understand environmental processes, calculate fluxes and mass budgets for the
various sédiment components, and study paleoclimate records. Presently, radiocarbon dating is considered more reliable than 210Pbex data for establishing accurate rates of sédiment accumulation in the Ross Sea [2,3], but they can be better
used together to overcome the effect of mixing [4,5].
This research, carried out within the framework of the Italian Programma
Nazionale di Ricerche in Antartide, is aimed at understanding the characteristics
of three représentative sites of the Ross Sea with respect to biogenic fluxes, sédiment composition and macrobenthos populations.
2 Study Area
The study area and the sampling locations are shown in Fig. 1. Frignani et al. [6]
described the network of processes that détermine the formation, transport and
fate of the particulate matter and its rôle in the biogeochemical cycles in the Ross
Sea. The biogenic components formed in the surface layer, which are not dissolved
or recycled, sink via fecal pellets, cellular débris and aggregates [7] and accumulate
in sédiments of areas where water dynamics is weak. Smith and Nelson [8] suggested that algal blooms resuit from vertical stability imparted by melting ice that
begins in the polynya close to the Ross Ice Shelf, and expands northward. The patterns of surficial sédiments [9,10] and satellite imagery [11] suggest phytoplankton biomass and production gradients west to east and south to north. The three
study sites, located along the south to north direction of retreat of the marginal ice
zone, were chosen to study particle fluxes through the water column using moored
instruments (sédiment traps, current meters, transmissometers). Site A, located in
south-west Ross Sea at 810-m depth, is important to understand particle transport
and sédiment accumulation in proximity to the Ross Ice Shelf. The area is made
interesting by the initial phase of the ice margin retreat and Smith and Gordon
[12] found that phytoplankton production was dominated by the prymnesiophyte
Phaeocystis antarctica, although significant numbers of diatoms co-occurred.
Mooring A, operative since January 1994, is the subject of a co-operation with the
US program ROAVERRS. Site B, located in the center of the northern part of the
Joides Basin at 580-m depth, represents a setting characterised by high biosiliceous
sédiment accumulation. Mooring B was first deployed in December 1994. Finally,
site C, in the northern flank of the Mawson Bank very close to the shelf break, is
représentative of an environment with high energy and reworked sédiment.
Mooring C was left in place from December 1994 to January 1996.