Early chemical diagenesis and sediment-water solute exchange in the East China Sea.

Measurements of pore water solute profiles, reaction rates, and sediment-water solute fluxes, together with associated studies of physical and biological characteristics of sedimentary deposits off the Changjiang River, demonstrate well-defined spatial patterns in diagenetic processes. High suspended matter, high rates of physical disturbance of the bottom and high net sedimentation near the river mouth inhibit primary production of organic matter in the water column and the establishment of a well-developed benthic community. Sediments in this region are relatively unreactive with respect to organic matter decomposition reactions compared to deposits underlying more productive regions along the edge of the river plume farther offshore. The presence of abundant infauna in offshore regions prevents the build-up of decomposition products, so that trends in average interstitial solute concentrations away from the river mouth are opposite to those expected on the basis of sediment reactivity alone. -from Authors