Distribution of Dissolved Iodine in the Irish Sea, a Temperate Shelf Sea

Abstract

The distribution of iodine in the Irish Sea in the summer of 1977 is described in terms of iodate and total iodine, rationalized to a salinity of 35 (practical salinity scale). Both variables show a shorewards decrease, with the greatest depletions occurring in the shallower and stratified waters associated with the ledges (<50 m) that flank the sea. In the east of Liverpool Bay an interconversion of iodate without concomitant loss of total iodine is attributed to bacterial activity in the remnants of the Mersey plume. Phosphate and iodine concentrations in the more open, and deeper parts of the sea did not correlate well. Assuming the small scale of the temporal variation in the Menai Straits to be representative of the sea as a whole, it is suggested that the iodine system changes much more sluggishly than is indicated by other studies. Thus, the Irish Sea being an enclosed and 'shallow' shelf sea, is less prone to 'winter overturn' encountered on an open shelf. It thereby offers the possibility of longer periods of interaction between the iodine and biological systems. The possible future use of a steady-state reactor model is explored.