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The role of colloids in providing a source of iron to phytoplankton Wells, Mark L.

Abstract

Iron-rich colloidal material was found to be associated with diatoms in the natural environment. To determine if this association could be important to the organism, the supply of iron from colloidal forms to phytoplankton was investigated. Laboratory bioassays with the marine diatom Thalassiosira pseudonana demonstrated that freshly precipitated colloidal iron could readily support diatom growth. However, when these colloids were aged or subjected to short periods of heating, the iron availability was drastically reduced. The iron availabilty was not increased with addition of the complexing agent EDTA. The reduction in availability appears to be linked to increased thermodynamic stability of the colloidal hydrous ferric oxides. The probable mechanism of this reduction is decreased colloidal dissolution rates. The supply of iron from colloids to phytoplankton appears to be determined by the chemistry of the colloidal iron material rather than by the physical association of colloidal iron and cell walls.

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