Journal
CONTINENTAL SHELF RESEARCH
Volume 89, Issue -, Pages 76-87Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.csr.2013.11.027
Keywords
Planktonic foraminifera; Water-column habitat; Oligotrophic area; Upwelling; Paleoceanographic proxies
Categories
Funding
- Fundacao de Amparo a Pesquisa do Estado de Sao Paulo-FAPESP [2002/06633-0]
- CAPES
- Conselho Nacional de Pesquisa CNPq
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The vertical distribution (0 to 100 m) of planktonic foraminifera was investigated based on 40 tow samples that were collected in eight stations, during the austral summer of 2002, in a geographically restricted area (23 degrees S-25 degrees S and 40 degrees W-44 degrees W) on the southeastern Brazilian continental margin. Species' abundances are low (less than 10 specimens/m(3)), which is typical of an oligotrophic area. The foraminifera assemblage is mainly composed of warm water species (Globigerinoides ruber white and pink forms), with a predominance of spinose and symbiont-bearing species. Temperature and inorganic nutrient enrichment of the surface are the main factors that control foraminiferal abundance and diversity; nevertheless salinity can also influence the ecological descriptors. The role of the deep chlorophyll maximum (DCM) in the distribution of foraminifera is not always clear, but the increase in the abundance of G. ruber (white and pink) seems to be related to a deeper DCM, and high salinities (S > 36.5). The ecological habitat of these species is affected by the depth of the mixed layer, with a predominance of the white form in deeper layers. Increases in the foraminiferal diversity are related to the dynamics of the Brazil Current system, which displaces the area of high productivity in the euphotic zone off the coast. The abundances of Globigerina bulloides, Globigerina falconensis, Globigerinella calida and Globigerinella siphonifera follow the nutrient enrichment of the surface water mass, corroborating the usefulness of these species as paleoproductivity proxies in the study area. These data confirm the use of diversity measurements and assemblages composition for reconstructing past water column structures in subtropical oceans. (C) 2013 Elsevier Ltd. All rights reserved.
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