Anoxic mineralization of biogenic debris in near-shore marine sediments Gulf of Trieste, northern Adriatic/

Anoxic degradation of sedimentary biogenic debris using closed incubation experiments was studied at two sampling stations in the Gulf of Trieste northern Adriatic.. Production rates of dissolved inorganic carbon DIC., NHq, PO3y and dissolved Si dSi., and reduction rates of SO2y were measured and anoxic mineralization rates were 4 4 4 modeled using a first order G-model and multi-G approach. The depth profiles of these rates revealed an exponential decrease indicating that the largest fraction of mineralization of biogenic debris and SO42y reduction occurs in the surficial sediment layer and on the sediment surface. Comparing the depth-integrated anoxic mineralization rates at both stations with benthic fluxes of DIC, NHq4 , PO43y and dSi measured at the in situ temperature in the dark, it appears that the DIC and PO43y fluxes are higher because the mineralization mostly occurs at the sediment]water interface, and that besides SO42y reduction, other electron acceptors are involved in the organic matter decomposition pathway in these surficial sediments. The NHq production was higher than the benthic fluxes because of NHq 4 4 oxidation. The production of dSi was in good agreement with benthic fluxes implying that temperature is the main factor of dSi production and benthic fluxes in these sediments.