The Bay of Bengal — A major nutrient source for the deep Indian Ocean

The distribution of nutrient elements and dissolved oxygen in the deep Indian Ocean suggests that the Bay of Bengal Fan sediment serves as a major nutrient element source and oxygen sink. The distribution of nutrient element excesses and oxygen deficiences away from the fan is consistent with diffusion along isopycnal surfaces with circumpolar deep water acting as a sink for nutrient elements and source for dissolved oxygen. In the course of the entire GEOSECS program only at the Bengal Fan station were nutrient element excesses and oxygen deficiencies (relative to the overlying water column) observed in the benthic mixed layer. The unique aspect of this station is likely the result of very high rates of respiration and particle dissolution coupled with a high stability of the water column overlying the benthic mixed layer.The chemical data show that for each mole of organic carbon oxidized 1.5 moles of CaCO₃ must dissolve and that for each mole of CaCO₃ dissolved about one mole of silica go into solution. The NO₃ and PO₄ excesses are about two thirds those predicted from the Redfield ratios (i.e., O₂ : NO₃ : PO₄ = 135 : 15 : 1).