Particulate iron and manganese in the Santa Barbara Basin,California |
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| Authors: | Alan M Shiller Joris M Gieskes N Brian Price |
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| Institution: | Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093 U.S.A.;Grant Institute of Geology, University of Edinburgh, West Mains Road, Edinburgh, Scotland EH9 3JW U.S.A. |
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| Abstract: | Particulate Fe and Mn may be important trace metal scavengers in the water column as well as being probable indicators of biologically mediated redox processes. A study has been made of suspended particulate composition in the Santa Barbara Basin, a shallow near-shore basin off southern California with sub-oxic conditions below sill depth. Observations have revealed several interesting phenomena relating to the geochemistry of Fe and Mn. Most striking is a profound enrichment of particulate Fe in samples from the bottom two hundred meters. These particulates have a constant Fe/P mole ratio of about three and may originate at the sediment-water interface or may be transported to the basin from local marshes. For particulate Mn, enrichments are observed both in the sub-sill waters and near the base of the euphotic zone. A consideration of particle removal rates suggests that the sub-photic zone enrichment has a biogenic origin. In the sub-sill waters, enrichment in Mn is apparently due to the precipitation of dissolved Mn diffusing from the anoxic basin sediments. A simple mass balance suggests that most of the Mn lost from the sediments is transported from the Santa Barbara Basin in dissolved form. |
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