To answer these questions we gather field samples from several oceanic regimes (Black Sea, Equatorial Pacific Ocean, the Arabian Sea and the Southern Ocean), collecting plankton, suspended particulate matter by filtration, sinking particles in sediment traps and sediment cores. By combining our lipid results with the amino acid data of Dr. Cindy Lee and the elemental and carbohydrate data of Dr. John Hedges we are able to develop a comprehensive picture of molecular-level organic biogeochemistry in the ocean.

We have found that there are significant variations in the flux and composition of lipid biomarkers in the water column of the ocean as a function of 1) surface water productivity, 2) the species composition of plankton in the surface waters, 3) diagenesis and remineralization of organic matter as it transits the water column towards the sediments, and 4) alteration processes at the water sediment interface. Despite the overwhelming dominance of marine derived lipids in particulate organic matter, sediments are significantly enriched in terrigenous lipids. This indicates a selective removal of most marine-derived lipids and a preferential preservation of terrigenous compounds.

Resolving these issues helps interpret and predict the cycles of global climate change and the role that the ocean may play in modulating the environment of Earth over geological time scales (i.e. 100's to 100,00's of years). Also, understanding contemporary biogeochemical processes provides a way to evaluate the sedimentary paleoenvironmental record and the processes by which organic matter is converted into fossil fuels (petroleum). Finally, while we focus primarily on naturally occurring compounds, these natural substances and the processes that determine their fates serve as models for predicting the behavior of anthropogenic contaminants (e.g. PCB's, PAH's, etc.) in marine ecosystems.

Selected References:

S.G. Wakeham and C. Lee. (1993) Production, transport, and alteration of particulate organic matter in the marine water column. In: Organic Geochemistry (M. Engel and S. Macko, eds.), Plenum Press, pp. 145-169.

S.G. Wakeham. (1995) Lipid biomarkers for heterotrophic alteration of suspended particulate organic matter in oxygenated and anoxic water columns of the ocean. Deep-Sea Res. 42: 1749 - 1771.

S.G. Wakeham, J.I. Hedges, C. Lee, M.L. Peterson and P.J. Hernes. (1997) Compositions and transport of lipid biomarkers through the water column and surficial sediments of the Equatorial Pacific Ocean. Deep-Sea Res. II. 44:2131-2162.

S.G. Wakeham, C. Lee, J.I. Hedges, P.J. Hernes and M.L. Peterson. (1997) Molecular indicators of diagenetic status in marine organic matter. Geochim. Cosmochim. Acta. 61:5363-5369.

C. Lee, D.W. Murray, R.T. Barber, K.D. Buessler, J. Dymond, J.I. Hedges, S. Honjo, S.J. Manganini, J. Marra, C. Moser, M.L. Peterson, W.L. Prell and S.G. Wakeham. (1998) Particulate organic carbon fluxes: Results from the U.S. JGOFS Arabian Sea Process Study. Deep-Sea Res. II 45:2489-2501.