Section outline

    • The cycle of organic iodine gas in seawater and sediments is summarized in Figure 5. (1) Phytoplankton absorbs iodide ions (I-) from seawater and then (2) settles to the sediment surface. (3) Iodic acid ions (IO3-), which are abundant in seawater, are reduced to I- at some depth in the sediment. (4) Diatom aggregates on the sediment surface produce ethyl iodide (C2H5I) and methyl iodide (CH3I) from I- in their bodies. (5) Diatom aggregates can also use the I- produced in the sediment to make these organic iodine gases. (6) I- in the sediment seeps into the water directly above. (7) C2H5I and CH3I that seep into bottom water are decomposed by microorganisms relatively quickly and their concentration is thought to decrease.

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