Suboxic mobile mud belts apparently characterize large portions of tropical continental shelves and may play a major role in global biogeochemical cycling and elemental storage. In this study, investigators from the State University of New York at Stony Brook will continue their past work on mobile mud belts off French Guiana downdrift of the Amazon River and initiate study with an international team on similar deposits on the shelf of Papua New Guinea.. There are three primary objectives: (1) to document, quantify, and model the cycling rates, reaction pathways, material source, and sedimentary storage of biogenic debris amd nutrients in the topmost 2 meters of seafloor; (2) to characterize the associations of benthic biological regimes with particular physical/sedimentological settings; and (3) to elucidate the authigenic mineral assemblages and biogenic structures characterizing these sediments. This work promises to significantly increase our current understanding of the roles played by these tropical sediment systems in the cycling of carbon, nutrients, and trace metals.