In Situ Rates of Sulfate Reduction and Volatile Organic AcidMetabolism in the Black Sea

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This project is focused on sulfate reduction rates in the anoxic water column and superficial sediments of the Black Sea. In combination with measured organic-carbon burial-rates in the sediment column, and input rates determined by ongoing sediment trap studies, the results will provide important quantitative information of rates and depth distributions of both carbon and sulfur cycling. Additional measurements of short-chain organic- acid-concentration distributions plus in situ radiotracer turnover rates in the water column and sediments should provide new insights concerning the roles of organic acids, particularly acetate, and other potentially significant intermediates. Water column rate measurements will be conducted by a field- tested instrument, the Sampler Incubation Device (SID), that is capable of performing all operations of sample procurement, radiotracer introduction, incubation, and time series withdrawal and fixation of subsamples directly in situ. Sediment rate measurements will be conducted using free-fall tripod vehicles. These vehicles will be equipped with newly developed sediment injectors that will permit the accurate in situ introduction of radiotracers in a continuous track from a depth of 10 cm through the surface and into the overlying fluff layer.