Sinking particulate matter is the major vehicle for exporting carbon from the sea surface to the ocean interior. During its transit towards the sea floor, most (usually >90%) of particulate organic carbon (POC) is returned to inorganic form and redistributed in the water column. This redistribution determines the depth profile of dissolved CO₂ , including its concentration in the surface mixed layer, and hence the rate at which the ocean can absorb CO₂ from the atmosphere. The ability to predict quantitatively and mechanistically the depth profile of remineralization is therefore critical to predicting the response of the global carbon cycle to environmental change.

Since 2002, and after several years of the Joint Global Ocean Flux Study (JGOFS) , we have been conducting an international field based project, MedFlux , in the northwestern Mediterranean Sea to address the hypothesis was that minerals produced by organisms, or introduced into the surface ocean by winds, critically influence carbon export to the deep ocean and sediments. This multi-tracer project is a collaboration between investigators in the US (Drs. Cindy Lee and Kirk Cochran at Stony Brook University) and Mr. Michael Peterson (University of Washington), France (Drs Madeleine Goutx and Christian Tamburini , University of Marseilles, France), Spain (Dr. Pere Masque (Autonomous University of Barcelona) and Monaco (Drs. Scott Fowler and Juan Carlos Miquel, Marine Environment Laboratory, International Atomic Energy Agency). We are investigating (1) whether ballast minerals physically protect a fraction of their associated total organic matter, and(2) whether the ratio of organic carbon to ballast is key to predicting variability in the export fluxes and sinking velocities of organic carbon. We are measuring simultaneously a suite of properties that are thought to be indicative of fluxes, and to synthesize these measurements using a variety of modeling and statistical techniques.

Selected References :


R. A. Armstrong, C. Lee, J. I. Hedges, S. Honjo and S. G. Wakeham (2002) A new, mechanistic model for organic carbon fluxes in the ocean based on the quantitative association of POC and mineral ballasts. Deep-Sea Res. II 49: 219-236.

S. G. Wakeham, M. L. Peterson, J. I. Hedges and C. Lee. (2002) Lipid biomarker fluxes in the Arabian Sea: with a comparison to the Equatorial Pacific Ocean. Deep-Sea Res. II. 49: 2265-2301.

C. C. Sheridan, C. Lee, S. G. Wakeham and J. K. B. Bishop. (2002) Suspended particle organic composition and cycling in surface waters and midwaters of the equatorial Pacific Ocean. Deep-Sea Res. 49: 1983-2008.

C. Lee, S. G. Wakeham and C. Arnosti. (2004) Particulate organic matter in the sea: the composition conundrum. Ambio 33: 565-575.

J. A. Brandes, C. Lee, S. Wakeham, M. Peterson, C. Jacobsen, S. Wirick, and G. Cody. (2004) Examining marine particulate organic matter at sub-micron scales using scanning transmission X-ray microscopy and carbon X-ray absorption near edge structure spectroscopy. Mar. Chem. 92: 107-121.

M. L. Peterson, S. G. Wakeham, C. Lee, M. A. Askea and J. C. Miquel. Novel techniques for collection of sinking particles in the ocean and determining their settling rates. (2005) Limnol. Oceanogr.: Methods 3, 520-532.

M. Goutx, S. G. Wakeham, C. Lee, M. Duflos, C. Guigue, Z. Liu, B. Moriceau, R. Sempéré, M. Tedetti, and J. Xue. Composition and degradation of marine particles with different settling velocities in the Northwestern Mediterranean Sea. Submitted to Limnol. Oceanogr. (see MedFlux web site).