Preliminary Evidence for Iodate Reduction in Bottom Waters of the Gulf of Mexico During an Hypoxic Event
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abstract
The distributions of iodate and total inorganic iodine concentrations in the waters on the Texas-Louisiana shelf in April, June, and August 2004 are described. Iodine-salinity graphs show three-end-member mixing involving onshore and offshore surface waters and deep offshore water. The April survey showed simple mixing on the surface, but in the later surveys, iodate concentrations were often much lower than predicted by the mixing curve while those for total inorganic iodine were higher. This demonstrated both iodate reduction in the water and iodide addition, although individual samples did not show equivalent speciation changes. Hydrographically, the system consists of the estuaries of the Mississippi and Atchafalaya rivers as they spill onto the shelf. The waters are stratified seasonally by a robust halocline, leading to hypoxia in the bottom waters from the combined effect of restricted downward diffusion of oxygen and the sinking of the luxuriant growth of phytoplankton induced by riverine nutrient supply. The distributions of iodate and total inorganic iodine are, therefore, interpreted in terms of water-sediment interaction as the shelf shoals to the north. 2011 Springer Science+Business Media B.V.
