Lipid biomarkers in deep sea sediments from the Campos Basin, SE Brazilian continental margin

Lipid biomarker distributions in surface sediments were determined using gas chromatography (GC) and GC–mass spectrometry (GC/MS) in order to evaluate the sources and distribution of organic matter (OM) in the slope of Campos Basin (southeastern Brazilian continental margin). Samples were collected with a box corer at 43 stations ranging from 750 m and 1950 m water depth and in two sectors of the slope. The concentrations of total fatty acids [FAs; 111–2305 μg g total organic carbon (TOC)−1], total sterols (19.6–747 μg g TOC−1) and total n-alcohols (7.9–328 μg g TOC−1) represented a decreasing gradient in comparison to shallow areas (40–500 m) in the same region. The greater contribution of plankton-derived lipids (e.g. short chain FAs and alcohols, phytosterols) than lipids from terrestrial sources (long chain FAs and alcohols) suggested a predominance in the sediments of OM derived from autochthonous processes in the water column. In this sense, the sedimentary OM may represent a significant source of energy for secondary benthic producers. However, principal component analysis (PCA) and source assignment of lipids revealed variations in OM composition on a regional scale, which probably related to topographic features and local oceanographic conditions. Such differences in the composition, and consequently in the bioavailable fraction, of OM should be accounted for in the characterization of the benthic communities in the slope of the Campos Basin.