My PhD abstract, or what I've been up to for the past four years...
The majority of iodine in seawater takes the form of iodate (IO3-), but in surface waters significant quantities of thermodynamically unstable iodide (I-) are observed and have been attributed to biological activity. In this thesis, experimental investigations of the influence of marine algae upon the reduction of iodate to iodide are presented alongside spatial and temporal surveys of dissolved inorganic iodine speciation in the Southern Ocean.
Laboratory incubations of microalgae showed the ability to reduce iodate to iodide was highly variable with algal species and more pronounced in two cold-water strains studied than three temperate strains. In the cold-water cultures 50 to 100% of the consumed iodate was converted to some other form, possibly dissolved organic iodine (DOI). A preliminary investigation into the measurement of DOI by ICP-MS was conducted. Attempts were also made to measure
particulate iodine: the molar I/C ratio in a diatom species was found to be < 5 x 10-5. In tidal pools, the brown macroalgae Fucus serratus appeared to facilitate light independent reduction of iodate to iodide, and to release stored iodide, while green macroalga of the genus Ulva did neither. Incubation experiments suggested four other macroalgae also produce iodide.
In the Scotia Sea and Drake Passage, surface iodide was typically very low, at 10 to 20 nM. Horizontal gradients in iodide distribution did not appear to be related to nutrient or chlorophyll a concentrations and were best explained in terms of physical oceanographic features. Subsurface iodide maxima associated with temperature minima were observed. Iodide levels were similarly low (< 10 nM) during winter and spring at Marguerite Bay, Antarctica, but gradually increased during the intense summer algal blooms to reach up to 60 nM. Iodide accumulation was strongly correlated with biological productivity. Field experiments also demonstrated the photochemical reduction of iodate to iodide.
Laboratory incubations of microalgae showed the ability to reduce iodate to iodide was highly variable with algal species and more pronounced in two cold-water strains studied than three temperate strains. In the cold-water cultures 50 to 100% of the consumed iodate was converted to some other form, possibly dissolved organic iodine (DOI). A preliminary investigation into the measurement of DOI by ICP-MS was conducted. Attempts were also made to measure
particulate iodine: the molar I/C ratio in a diatom species was found to be < 5 x 10-5. In tidal pools, the brown macroalgae Fucus serratus appeared to facilitate light independent reduction of iodate to iodide, and to release stored iodide, while green macroalga of the genus Ulva did neither. Incubation experiments suggested four other macroalgae also produce iodide.
In the Scotia Sea and Drake Passage, surface iodide was typically very low, at 10 to 20 nM. Horizontal gradients in iodide distribution did not appear to be related to nutrient or chlorophyll a concentrations and were best explained in terms of physical oceanographic features. Subsurface iodide maxima associated with temperature minima were observed. Iodide levels were similarly low (< 10 nM) during winter and spring at Marguerite Bay, Antarctica, but gradually increased during the intense summer algal blooms to reach up to 60 nM. Iodide accumulation was strongly correlated with biological productivity. Field experiments also demonstrated the photochemical reduction of iodate to iodide.
posted by iodinegirl at 9:56 PM
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