Collaborative Proposal: Mineral Ballast and Organic Matter Compositions as Determinants of Particle Settling Velocities and Fluxes in the Sea (MedFlux)

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ABSTRACTOCE-0622754 / OCE-0622930 / OCE-0623271With support from this grant, the members of the MedFlux research team at SUNY-Stony Brook, Skidaway Institute of Oceanography, and University of Washington will complete data analysis and informational synthesis their pioneering study of the fate of biogenic particles falling from the oceanic euphotic zone. The central focus of the MedFlux, which began with NSF support four years ago, is to develop a better mechanistic understanding of the "ballast hypothesis," which states that Particulate Organic Carbon (POC) fluxes to the deep ocean and sediments are directly proportional (3-7% OC by weight) to fluxes of "ballast minerals" produced by organisms (opal or carbonate minerals) or introduced into the surface ocean by physical processes. Earlier work (Armstrong et al. 2002; Klaas & Archer 2002) showed that the flux of organic carbon at depth can be predicted extremely well (85-90% explained variance) by ballast flux; the types and amounts of mineral ballast introduced to the surface ocean may therefore be critical determinants and predictors of the ocean's ability to take up and store carbon. To advance these studies, the research team also developed specialized sampling devices and protocols for measuring the two fundamental components of flux: particle concentration C(z) and average sinking velocity w ( z) at depth z. With funding under this grant, the team will be able to evaluate fully both the scientific output of the project as well as the performance of the new particulate sampling technology.This research has a number of broader impacts for for global carbon cycle and environmental change issues. For example, as pH decreases in response to the continued dissolution of anthropogenic carbon dioxide in the ocean, carbonate minerals may dissolve preferentially, affecting both ballasting and the average remineralization depth of POC in the ocean. This situation would necessitate a mechanism-based understanding of POC ballasting in the ocean. Additionally, MedFlux work will continue to foster international collaborations among three U.S. universities and colleagues in Monaco, France, Spain, and Geermany. The project also provides for the support and training of graduate students.