Primary production processes in ice-free waters of the Ross Sea (Antarctica) during the austral summer 1996

During austral summer 1996 (January 11–February 10) oceanographic studies were conducted in the ice-free waters of the Ross Sea within the framework of the Italian National Programme for Antarctic Research (PNRA). Thirty-eight hydrological stations within 72.5°–78.0°S and 164.5°E–175.0°W were sampled. Size-fractionated photosynthetic pigments were measured at all stations, primary production was evaluated at 24 stations, and P vs. E measurements were carried out at 3 or 4 depths at 18 stations. In the open Ross Sea, integrated chlorophyll a (Chl a) concentrations were between 15 and 102 mg m −2 in the 0–100 m layer, and primary production was between 124 and 638 mgC m −2 d −1. Offshore waters were completely ice-free and the water column was only slightly stratified. However, phytoplankton biomass and production were relatively high wherever the Upper Mixed Layer (UML) was