Dissolved vanadium on the Louisiana Shelf: effect of oxygen depletion

New measurements of dissolved vanadium in waters of the Louisiana Shelf aff ected by outflow from the Mississippi/Atchafalaya River system are presente d here. These measurements complement previously published estuarine vanadi um data and allow a reexamination of prior conclusions. In estuarine and co astal regions it appears that the most significant vanadium depletions occu r in association with reducing conditions. These reducing conditions are fr equently driven by anthropogenic eutrophication. Sedimentary inputs also ap pear to be a factor in affecting the flux of vanadium to the ocean in certa in environments In contrast to previous results we find no compelling evide nce of biological removal of vanadium from estuarine surface waters. Given the uncertainties, it is difficult to accurately estimate the natural flux of dissolved vanadium from the land to the open ocean. Nonetheless, increas ing coastal anthropogenic eutrophication could substantially alter the natu ral fluvial vanadium input as well as possibly shift the primary locus of o ceanic vanadium removal. (C) 1999 Elsevier Science Ltd. All rights reserved .