Palucci, Antonio¹, Olga Mangoni², Roberto Barbini¹, Gian Carlo Carrada², Francesco Colao¹, Roberta Fantoni¹, Luca Fiorani¹, Monica Modigh³ and Vincenzo Saggiomo³

¹ENEA, FIS-LAS, Via Fermi 45, 00044 Frascati, Italy, Tel: +39(06)94005299, Fax: +39(06)94005312, E-mail: palucci@frascati.enea.it, ²University of Naples “Federico II”, Naples, Italy and ³Zoological Station “A. Dohrn”, Naples, Italy

New estimates of primary production in the Ross Sea derived from in situ, lidar and satellite data

During the austral summer 2001 (January 11 February 19) an oceanographic cruise was carried out in the Ross Sea within the framework of the Italian National Programme for Antarctic Research (PNRA). Exceptional pack-ice coverage was encountered over large areas of the study area. Spatial and temporal distribution of phytoplankton biomass (Chla), in situ simulated ¹⁴C primary production and ¹⁴C photosynthetic parameters (PvsE experiment) were studied in several stations in coastal and offshore waters. Moreover, a lidar fluorosensor provided a continuous stream of data on the bio-optical properties of the crossed sea regions. In particular, the turbidity and the concentration of Chla and chromophoric dissolved organic matter (CDOM) were measured. The entire Ross Sea was characterized by a high variability in phytoplankton biomass distribution both in temporal and spatial terms. In contrast, photosynthetic parameters (P^B_max, á, E_k) vary within narrow ranges, with a marked photoacclimation to low levels of irradiance (E_k from 8 to 56) and mean P^B_max of 1.2 mgC (mg Chl)^-1. Simulated in situ ¹⁴C primary production was well correlated with the productivity calculated with the photosynthetic coefficients obtained from PvsE experiment and thus allowed the calculation of primary production from surface Chla concentration and irradiance over the entire Ross Sea. Moreover, the integration of the information gathered from stations and lidar lead to a regional calibration of the SeaWiFS bio-optical algorithm and, hence, to corrected satellite thematic maps of primary production. Our results suggest that SeaWiFS estimates of primary production in the Ross Sea should be reviewed.