Lipid biomarkers in surface sediments from an unusual coastal upwelling area from the SW Atlantic Ocean Marcos Y. Yoshinaga a, * , Paulo Y.G. Sumida a , Stuart G. Wakeham b a Oceanographic Institute, University of São Paulo, Praça do Oceanográfico, 191 São Paulo, CEP 05508-120, Brazil b Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, GA 31411, USA article info Article history: Received 15 March 2007 Received in revised form 22 June 2008 Accepted 6 July 2008 Available online 22 July 2008 abstract The coastal upwelling off Cabo Frio (SE Brazilian coast, SEBC) represents an exception to the world’s oceans since the majority of the upwelling areas are located in eastern boundary current systems. Cabo Frio represents an interesting area for investigation due to its tight physical–biological interaction and the importance of the region as a major fishery area in the SEBC. We analyzed a suite of lipid biomarkers to apportion the main sources of organic matter in surface sediments of the continental shelf off Cabo Frio, comparing the area to non-upwelling regions off the SEBC (shelf break off Cabo Frio and continental shelf off Uba- tuba). During spring and summer (the upwelling period), diatoms are probably the major sources of polyunsaturated fatty acids (PUFAs) and C 28 sterols in surface sediments from Cabo Frio continental shelf. Sediments sampled in winter showed, in contrast, lower rela- tive abundance of PUFAs and higher stanol/stenol ratio values. In deeper regions off Cabo Frio, elevated concentrations of alkenones, 24-methylcholest-5,22E-dien-3b-ol and 24-eth- ylcholest-5-en-3b-ol during the spring may be produced by prymnesiophytes or crypto- phytes and cyanobacteria, respectively. In Ubatuba, the C 27 and C 28 sterols are likely derived from omnivorous salps and nanoflagellates. At non-upwelling areas, despite the increase in biomarker concentrations during spring and summer, lower concentrations of PUFAs, phytol and algal sterols than in shelf areas off Cabo Frio suggest the importance of the upwelling system to the rapid transfer of organic carbon to surface sediments. Our results suggest that spatial and temporal variability in organic matter production and deposition merits consideration for constraining the carbon budgets in the coastal region off Cabo Frio. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Lipid biomarkers can provide valuable information regarding the origin, transport pathways and alteration and transformation processes of organic matter (OM) as a result of their greater preservation potential in aquatic environments than other major biogeochemical classes (e.g. DNA, carbohydrates and proteins; see Wakeham et al., 1997a). In addition, the diversity of molecular struc- tures makes possible the attribution of specific compounds to specific organisms (Volkman, 2006). The understanding of lipid distributions in modern sediments allows their use as proxies for paleoenvironmental, including paleoclimatic, reconstruction (Dahl et al., 2004; Pancost and Boot, 2004). Lipids represent a major organic carbon pool in phyto- plankton and, although they represent only a small fraction of sedimentary organic carbon, they are widely applied to evaluate biogeochemical and diagenetic processes in marine sediments (Volkman et al., 1987, 1998; Belicka et al., 2004). Coastal upwelling systems provide environ- ments well suited to the analysis and utilization of bio- marker tracers owing to elevated primary productivity and high rates of sedimentation of labile autochthonous 0146-6380/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.orggeochem.2008.07.006 * Corresponding author. Present address: Organic Geochemistry Group, MARUM, University of Bremen, 28334 Bremen, Germany. Tel.: +49 421 21865744; fax: +49 421 21865715. E-mail address: marcosyukio@gmail.com (M.Y. Yoshinaga). Organic Geochemistry 39 (2008) 1385–1399 Contents lists available at ScienceDirect Organic Geochemistry journal homepage: www.elsevier.com/locate/orggeochem