Benthic foraminiferal assemblages of the South Brazil: Relationship to water masses and nutrient distributions |
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| Authors: | PPB Eichler BK Sen Gupta BB Eichler ES Braga EJ Campos |
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| Institution: | 1. UNISUL—Universidade do Sul de Santa Catarina, Av. Pedra Branca 25, Palhoça, SC 88132-000, Brazil;2. Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803-410, USA;3. Instituto Oceanográfico, Universidade de São Paulo, Praça do Oceanográfico 191, CEP 05508-900, Cidade Universitária, São Paulo, SP, Brazil |
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| Abstract: | Using distributions of benthic Foraminifera and bottom-water variables (depth, salinity, temperature, oxygen, suspended matter, organic matter, phosphate, silicate, nitrite, and nitrate), we investigated movements of water masses on the South Brazilian Shelf (27–30°S) and assessed the seasonality of continental runoff on the distribution of shelf water masses. The data were obtained from water and sediment samples collected in the austral winter of 2003 and austral summer of 2004 in three transects. The terrestrial nutrient input was significantly reduced at stations away from the coast, but high values of nutrients were maintained in subsurface waters due the presence of South Atlantic Central Water (SACW) at greater depths. At shallow sampling stations the influence of freshwater runoff was related to (1) the dominance of calcareous benthic Foraminifera, such as lagoon-related Pseudononion atlanticum, Hanzawaia boueana, Bulimina marginata, Bolivina striatula, Elphidium poeyanum, together with several agglutinated species, including Arenoparrella mexicana, Gaudryina exilis, and Trochammina spp., common in coastal environments subject to wide salinity fluctuations. In contrast, smaller forms and higher species diversity characterized the assemblage at offshore stations. In winter, the presence of Buccella peruviana and Uvigerina peregrina at Santa Marta Cape suggest the possible transport of those species of Subantarctic Shelf Waters (SASW) origin. Foraminifera associated to Subtropical Shelf Water (STSW) were dominated by Globocassidulina subglobosa in both seasons. In summer, the occurrence of U. peregrina in the shallower stations suggested the influence of SACW nutrients brought up by upwelling of deeper waters. |
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| Keywords: | OM organic matter SM suspended particulate matter CW coastal water PPW Plata plume water SACW South Atlantic Central Water SASW Subantarctic Shelf Water STSW Subtropical Shelf Water TW tropical water SBB South Brazil Bight SBS South Brazilian Shelf |
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