MEDFLUX: Association of Organic Matter With Ballast Minerals in Sinking Particles

Recently we hypothesized that ballast minerals on sinking particles physically protect a fraction of their associated organic matter, and that the ratio of organic carbon to ballast is key to predicting variability in export fluxes and sinking velocities of organic carbon as estimated using radiotracers. To test this idea we collected sinking particles using sediment traps at the French JGOFS DYFAMED site in the western Mediterranean. We measured organic and inorganic carbon, and biogenic and total Si, Ca, Al and Ti, to characterize the organic and inorganic material in the particles. Using traditional assumptions to estimate organic matter, CaCO3, biogenic opal and the lithogenic fraction, we found that 20-30% of the material was unaccounted for. We will make wild and unsubstantiated speculations on what this material might be and how it might affect particle density.