THE RELATIONSHIP BETWEEN DISSOLVED ORGANIC-CARBON (DOC) AND FLUORESCENCE IN ANOXIC MARINE POREWATERS - IMPLICATIONS FOR ESTIMATING BENTHIC DOC FLUXES

Fluorescence and dissolved organic carbon (DOC) measurements of porewa ters from the Santa Barbara Basin, the Guaymas Basin, and the upper se ctions of the Nankai Trough suggest that ultraviolet fluorescence (lam bda(ex) = 325 nm, lambda(em) = 450 nm) may be used as a first order es timate of DOC in anoxic marine porewaters. The majority of porewater o rganic carbon appears to be fluorescent, while a constant approximatel y 1 mM DOC, probably the low molecular weight compounds, is not fluore scent. These data are consistent with a model in which low molecular w eight compounds dissolved in porewater act as the common intermediate between labile sedimentary organic matter and remineralization or poly merization products. Fluorescence may also be used to sensitively esti mate benthic DOC fluxes to the overlying water column. Results from th e Santa Barbara Basin, if representative of global anoxic oceanic regi ons, indicate that DOC release from anoxic sediments is not a major so urce of oceanic DOC when compared to internal recycling rates, but may be comparable to external input or permanent removal processes.