Recherche - Observatoire océanologique de Banyuls sur mer
Laboratoire Arago

 Elisabet SANE (Institut de Ciéncies del Mar-CSIC. Barcelona, Spain) présentera un séminaire le Vendredi 4 Février 2010 à 14h00 (Amphithéâtre A. Guille / Bat B 1er étage) portant sur le thème :

Organic matter in sediments of Antarctic continental shelves under the influence of climate change

In 1995 and 2002, 4200 km2 and 3200 km2 of the sections A and B of the Larsen Ice shelf disintegrated, respectively (Rack and Rott, 2004). During austral summer 2006-2007, five sediment cores were recovered from the Eastern Antarctic Peninsula (EAP) continental shelf. Pigments, amino acids, fatty acids, total proteins, total carbohydrates, total lipids and biogenic silica analyses were carried out, together with diatom microscopic observations, to investigate whether the drastic changes at the sea surface in EAP may be reflected in the sedimentary record. Excess 210Pb activity was measured to develop a radiochemical chronology of the sedimentary events. A sharp decrease in the concentration of pigments and in the number of diatom valves was observed below 2 cm depth.

This evident difference between the upper 2 cm of sediment and the deeper part of the sediment column was attributed to the drastic change in the upper water column conditions after the ice shelf collapses, which allowed the arrival of phytoplankton debris and fresh organic matter to the seafloor in EAP. The presence of bacterial-, zooplankton- and detrital-related FA throughout EAP cores and the high concentration of total carbohydrates in the deeper part of the sediment column suggest that there has been an input of older, more refractory organic matter into the region, presumably by lateral transport, before Larsen ice shelves  disintegration.