Rossmize expedition (1994-95): Zooplankton ecology

The ROSSMIZE Cruise, from 2 November 1994 to 3 January 1995 covered a wide stretch of the Western sector of the Ross Sea, from South to North (Lat. 71°56' to 76°30'S). The area investigated included: 1) a first group of stations located along the Ross Sea Ice Shelf, 2) a second large group of stations between the longitudes 180° and 170° W and from the barrier of the Ross Sea Ice Shelf up to the continental slope (around Lat. 72°S), 3) a third group in front of Cape Adare, 4) a final group in Terra Nova Bay (Fig. 1, Tab. 1). The cruise was made on board the R/V Italica, jointly organized with the US team of the R/V Palmer, and represents one of the first oceanographic cruises ever carried out in the Ross Sea during the austral spring. The scientific results obtained during a preceding 1989-90 cruise had emphasised that phytoplankton productivity in this region was greatly influenced by ecohydrodynamic processes occurring in the ice edge area (Hecq & Guglielmo, 1992; Hecq et al., 1992, 1993). It was shown that ice melting and retreat in the Ross Sea, propagating from the South to the North (Polynya), strongly increased the extension of the productive marginal ice zone (Fig. 2). This greatly influences the global productivity in the area favouring intense phytoplankton blooms in the water column. The algae contained in the ice are released by melting, mixed in the upper layers of the water column and consumed by grazing zooplankton. With the specific aim of better understanding this aspect of the ecology of the Ross Sea, a mutidisciplinary study was developed to take into account the main physical, chemical and biological features of the area, integrating experimental, field and prediction model studies. The programme focused on the following topics: nutrient distribution and dynamics, new and regenerated production, role of mesozooplankton, krill and top predators in controlling primary production, biochemical composition and fate of particulate organic matter, biogenic flux in the water column, biogenic sedimentation and seafloor bioturbation.