Cocolitóforos en sedimentos marinos frente a la entrada occidental del Estrecho de Magallanes (53°S) revelan cambios en la productividad durante los últimos 30.000 años

Abstract

We present a new record of coccolithophore (coccoliths) export productivity for the past 30,000 years based on the study of a marine sediment core collected at the western entrance of the Strait of Magellan (Core MD07-3128; 53°S, 75ºW). This sediment core revealed the presence of an assemblage composed by thirteen coccolithophore taxa, dominated by small Gephyrocapsa (>80% of the total assemblage on the average) and accompanied, in less proportions (1-10%), by two morphotypes of Emiliana huxleyi, Coccolithus pelagicus and Calcidiscus leptoporus. Coccolith concentration and CaCO3 content were strongly correlated (P << 0.01; R2 = 0.63). In general, both records were in phase with alkenone-derived sea-surface temperature (Caniupán et al., 2011) where maximum values of CaCO3 (>30%) and coccolith abundance (~109 coccoliths g-1 dry sediment) coincided with relatively warm periods (e.g., the Holocene). We found marked differences when comparing our data with a coccolith record published by Saavedra-Pellitero et al. (2011) for ODP Site 1233 at 41°S: At ODP Site 1233, coccolithophore production was maximal during the Last Glacial Maximum in response to the northward advection of macronutrients by the Antarctic Circumpolar Current. In contrast, site MD07-3128 experienced a reduction in coccolithophore production at the time, probably related to the negative effect exerted by the high inputs of terrigenous material and meltwater from the then nearby located large Patagonian Ice Sheet.