Sedimentary Pore Water DOC:Fluxes and Molecular Composition

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The flux of pore water DOC to overlying waters and the cycling of DOC within sediments are important but poorly constrained components of the oceanic carbon cycle. Preliminary pore water work and in situ benthic tripod flux estimates suggest three hypotheses: 1) marine sediments are an important source of water column DOC, 2) a component of the flux contributes to the refractory water column DOC pool, and 3) A component of the flux may be oxidized near the sediment water interface. The first hypothesis will be tested by using a benthic tripod to accurately measure this flux along a depth gradient reaching across the shelf to upper slope. The second hypothesis will be tested by pooling the overlying water in the flux tripod at the end of several deployments to form an ultrafiltered large volume sample that we will characterize at the molecular level and compare to similarly characterized water column DOC. An in situ dialysis sampler to sample for pore water DOC concentration and in situ oxygen concentration manipulation experiments will test the third and all will take place along the Pacific Northwest cost, off the northwest coast of Mexico and in the Puget Sound.