Disponibilidade e distribuição dos nutrientes e clorofila - A nas águas adjacentes a península antártica

Abstract

The Antarctic ecosystem has long been characterised as a region with high nutrient concentrations and low Chlorophyll concentration, in what constitutes the antarctic paradox . However, many authors have shown that despite the low concentration of phytoplankton in some regions, this biomass may be high in others, especially if it is associated with lower depth waters causing an water mixture zone or upwelling with no nutrient depletion. To carry out this investigation, water was collected in depths varying from the near surface to 200 metres in the Sea of Weddell, the Sea of Bellinshausen, in the Strait of Gerlache and in the Straight of Bransfield in operations XXI, XX and XXI, Summers of 2000/01, 2001/02 and 2002/03, on the oceanographic vessel Ary Rongel. The nutrient dynamic was quite different in the areas sampled, with Chlorophyll-a values ranging from below detection to high values of 15x10 μg/L, such as in the Straight of Gerlache. Dissolved Inorganic Nitrogen (DIN) and Silicate had similar variations and have high values even when no noticeable consumption of these nutrients by primary production. It was expected that Phosphate would have a similar distribution as that of DIN and Silicate but in some regions, the high Phosphate concentrations coincided with higher values of Chlorophyll-a, and in one specific region of the Sea of Weddell, very low concentrations of Phosphate coincided with very low values of Chlorophyll-a which led us to believe in a certain control of primary productivity by Phosphorus. The different nutrient distribution found in the areas studied show us various subsystems, where conditions vary according to local depth proximity to islands or the continent, wind regime, ice cover, among other physical, chemical and biological variables. The project of this investigation currently is under the Grupo de Oceanografia de Altas Latitudes (GOAL), of Rede 1 (Antártica, Mudanças Globais e Teleconexões com o Continente Sul-americano) of the Brazilian Antarctic Program (PROANTAR). GOAL proposes a systematic sampling and analysis plan of physical, chemical and biological components of the Austral Ocean in order to contribute to relevant processes investigation, to understand the impact of global changes in this ecosystem as well as possible connections with the coastal zone of Brasil.