ON THE INTERPLAY BETWEEN HYDRODYNAMICS, BOTTOM MORPHOLOGY, SEDIMENTARY PROCESSES AND BENTHIC FORAMINIFERA ASSEMBLAGES IN THE SÃO PAULO BIGHT (BRAZIL, SW ATLANTIC)

Cintia Yamashita, Renata Hanae Nagai, Maria Virgínia Alves Martins, Thaisa Marques Vicente, Silvia de Mello e Sousa, Fabrizio Frontalini, André Palóczy, Michel Michaelovitch de Mahiques, Sueli Susana de Godoi, Isabel Montoya-Montes, Rubens Cesar Lopes Figueira

Abstract


Surface sediment samples recovered in the São Paulo Bight (SW Atlantic) were collected between 45 to 1132 m water depths to characterize sedimentary processes based on a multiproxy approach. This study analysis benthic foraminifera and abiotic data, including granulometry, TOC and C/N values. Spatial and yearly distributions of ocean chlorophyll-a concentrations [Chl-a] evaluated from available SeaWiFS Chlorophyll Ocean Colour Images also were analyzed. On the basis of the non-metric Multidimensional Scaling analysis two regions with different characteristics were identified (1) São Sebastião Island and (2) Grande Island. The C/N results indicate that in most of the studied stations the organic matter supplied to the sea bottom is provided essentially by oceanic productivity. Concentrations of chlorophyll-a and TOC are higher in Grande Island region than in the São Sebastião Island sector. In the first region the benthic foraminifera assemblages are larger but less diversified than in São Sebastião Island sector. The foraminifera assemblages of Grande Island region are dominated by Globocassidulina subglobosa and composed mostly by opportunist species related to episodic availability of food inputs related to the Cabo Frio upwelling system. The influence of this system seems to decrease in São Sebastião Island sector. In the deeper slope stations of the São Sebastião Island region, the presence of an arborescent community (Rhadammina spp. and Rhizammina spp.) and Nodulina dentaliniformis suggests that the sedimentary regime is relatively more stable and contain a higher amount of refractory organic than in Grande Island region for the similar range of depths.


Keywords


benthic foraminifera, chlorophyll-a concentrations, TOC, C/N, upwelling system, continental margin

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