The role of early diagenesis in the sedimentary steroids around Penguin Island, Antarctica

Abstract

The role of lipids in polar environments is of primary importance for understanding the cycling of carbon organic and associated elements. Thus, the knowledge of the nature and quality of organic matter is necessary to evaluate the overall impact in this area and to model the carbon cycle. The aim of this study was to determine the transformations of organic matter in the marine environment by analysis of a specific group of lipid biogeochemical markers, the sedimentary steroids. Sediment cores were collected during the 2007/08 austral summer in the vicinity of the Penguin Island (2 cores). In general, the cores were sectioned at 1 cm intervals and the steroids analyzed by gas chromatography with flame ionization detection (GC-FID), after Soxhlet extraction, adsorption column chromatography and derivatization. The results showed that organic matter had been subjected to extensive degradation and transformation with depth in the two corers and the general increase of the stanol/ stenol ratio may have represented the progressive reduction of stenols to stanols within the deepest sediment layers. According to the linear regression (R2) applied, the process at Penguin Island is governed by a natural supply, and a random pattern in the concentration values with increasing depth. These results contribute to the understanding of the current processes of organic matter transformation in this important region of Antarctic environment.