Distribution of coccoliths in surface sediments from the southwest Atlantic Ocean in relation to environmental gradients

Abstract

Coccolith compositions of surface sediment samples from the Southwestern AtlanticOcean were analysed in relation with present-day surface-water environmental parameters(temperature, salinity, phosphate, and nitrate). This work is based on surface sedimentdata sets obtained from the Argentinean Continental Margin (40 – 55°S and 55 – 65°W).A multivariate ordination technique, Redundancy Analysis, was applied on the relativeabundances of the most abundant taxa (Emiliania huxleyi, Gephyrocapsa muellerae,Calcidiscus leptoporus and Gephyrocapsa spp. small). The results of the analysis revealedthe affinities of G. muellerae and Gephyrocapsa spp. small for high nutrient conditions. Incontrast, E. huxleyi and C. leptoporus seem to be associated with high salinity and hightemperature. Statistical analysis results revealed three Groups (I–III), nutrient contentcontrolled. Group I lies within northern sites, is dominated by E. huxleyi and has a positivecorrelation with salinity and temperature. Conversely, Group II, located in SloggettCanyon, is dominated by E. huxleyi and is not correlated to any environmental variables.Group III, is composed by E. huxleyi and G. muellerae, is geographically confined to thesoutheast area and has a positive correlation with phosphate and nitrate. There wouldbe a moderate association of certain groups of coccolithophores (as Gephyrocapsa spp.)with nutrient-rich waters from the Malvinas Current, and Emiliania huxleyi strains moreassociated with relatively low nutrient content of waters from the northernmost part ofArgentinean Continental Margin.