Transformation of iodate to iodide in marine phytoplankton driven by cell senescence.

Bluhm, Katrin, Croot, Peter, Wuttig, Kathrin and Lochte, Karin (2010) Transformation of iodate to iodide in marine phytoplankton driven by cell senescence. Open Access Aquatic Biology, 11 (1). pp. 1-15. DOI 10.3354/ab00284.

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Previous studies have suggested that phytoplankton play an important role in the biogeochemical cycling of iodine, due to the appearance of iodide in the euphotic zone. Changes in the speciation of iodine over the course of the growth cycle were examined in culture media for a variety of phytoplankton taxa (diatoms, dinoflagellates and prymnesiophytes). All species tested showed the apparent ability to reduce iodate to iodide, though production rates varied considerably between species (0.01 to 0.26 nmol l–1 µg–1 chl a d–1), with Eucampia antarctica the least and Pseudo-nitzschia turgiduloides the most efficient iodide producers. Production was found to be species specific and was not related to biomass (indicated by e.g. cell size, cell volume, or chl a content). In all species, except for the mixotrophic dinoflagellate Scrippsiella trochoidea, iodide production commenced in the stationary growth phase and peaked in the senescent phase of the algae, indicating that iodide production is connected to cell senescence. This suggests that iodate reduction results from increased cell permeability, which we hypothesize is due to subsequent reactions of iodate with reduced sulphur species exuded from the cell. A shift from senescence back to the exponential growth phase resulted in a decline in iodide and indicated that phytoplankton-mediated oxidation of iodide to iodate was likely to be occurring. Iodide production could not be observed in healthy cells kept in the dark for short periods. Bacterial processes appeared to play only a minor role in the reduction of iodate to iodide.

Document Type: Article
Keywords: Plankton; Chemistry; Iodine speciation; Iodide; Iodate; Antarctic diatoms; Nitrate reductase; Glutathione; Sulphur species; Cell senescence
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BI Biological Oceanography
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.3354/ab00284
ISSN: 1864-7790
Date Deposited: 01 Nov 2010 12:16
Last Modified: 04 Jul 2019 13:10

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