A comparison of dissolved iodine cycling at the Bermuda Atlantic Time-series Station and Hawaii Ocean Time-series Station

The results of analyses of samples from the Bermuda Atlantic Time Series (BATS) and Hawaii Ocean Time-series (HOT) for dissolved iodine speciation are presented. At both sites iodate is reduced to iodide in surface waters by biological processes, but the iodide concentrations in the upper 100 m at the HOT site are approximately twice those at the BATS site. Using published estimates of surface water residence times and primary productivity at each station we use the differences between the two sites to derive an estimate of the in situ rate of iodide oxidation and the relationship between iodate reduction and primary production using a simple mass balance model. The model results suggest that on an annual basis iodide oxidation is relatively fast (half-life about 70 days) and that biological iodate reduction to iodide is about 100 times faster than iodide incorporation into particulate organic carbon.