HIDROQUÍMICA DE MASSAS D'ÁGUA OCEÂNICAS EM REGIÕES DA MARGEM CONTINENTAL BRASILEIRA, BACIA DE CAMPOS, ESTADO DO RIO DE JANEIRO, BRASIL

Abstract

This study is part of the Characterization of Deep Waters in the Campos Basin Project, formally coordinated by Cenpes/Petrobras in association of eight universities. Here, water samples from the southern Atlantic Ocean in the Campos Basin (RJ) - at Albacora Leste (Northern Area) and Barracuda and Caratinga (Southern Area) oil fields -, were characterized for their hydrochemistry. The water samples were collected in May 2002 in profiles (9-11 points) distributed in six isobaths from ~700 to ~1,700 m, totaling 12 sampling stations. The following variables were analyzed: temperature, salinity, dissolved oxygen, pH, nitrogen (N-NO 3 - , N-NO 2 - , N-NH 3 +NH 4 + ), phosphorus (P-PO 4 -3 , P-total), silicate (Si-SiO 2 ), suspended particulate matter (SPM), chlorophyll a, and dissolved and particulate organic carbon (DOC and POC). The waters were characteristically oligotrophic with a low contribution of COP in the SPM, a1%. In general, the water chemistry was more variable along the water column than horizontally, likely resulting of physical (thermal stratification, light attenuation) and biological processes (ex., production and mineralization). In relation to surface waters, above 200 m depth, deep waters were higher in nutrient concentrations and lower in SPM, POC and chlorophyll a. Horizontally, hydrochemistry variations were less apparent, suggesting some homogeneity over the areas of study. However, (C:N) a and C:Chlorophyll (μmol μg -1 ) ratios indicated some heterogeneity in the nutritional status of phytoplankton growth between the studied stations. Yet, differently of Albacora Leste, where no correlation between POC and chlorophyll a was observed, in Barracuda and Caratinga we found a trend of negative correlations between these variables. As a whole, these results indicate that more and complementary studies related to physiological and organic matter biogeochemistry are needed to improve our knowledgement on the structure and function of those waters.