Geochemical differences between planktic foraminifera morphotypes from Brazilian continental margin

Abstract

Recently, several molecular studies in planktic foraminifera demonstrated that morphospecies recognised nowadays are in fact composed of two or more species, cryptic species. This investigations have been developed on recent specimens collected on the water column with presence of biological material for performing such studies. Nevertheless, in sediment samples only the shells of the individuals are preserved, making molecular studies not possible for analysing which species are present on the sediment. In this case, individuals may be analysed in relation to its ecology. Although not always speciation is accompanied of distinct ecologic preference, most of the paleoceanographical studies are based on ecological differences between species. Therefore, for paleoceanographic interpretations its very important to identify individuals morphologic distinguishable and ecologicaly distinct in the sediment. For that end, one of the possible alternatives is to analyse the geochemistry from the planktic foraminifera shell. The present study proposes the oxygen and carbon stable isotope analysis (d18O e d13C) in individual shells of morphologic groups of planktic foraminifera morphometrically defined. There will be utilized planktic foraminifera from core tops and a box core from the brasilian continental margin to perform a latitudinal analysis and a single piston core to perform a temporal analysis of the planktic foraminifera ecology from this region. (AU)