Iodate and Iodide Distributions in the Waters of a Stratified Estuary

Speciation and distribution of inorganic iodine in the highly stratified Krka estuary (east coast of the Adriatic Sea) were investigated in the period from December 2000 to April 2001. Conservative behavior of total inorganic iodine was confirmed during the investigated period, but significant temporal and longitudinal variations were also observed. Concentrations of iodate and iodide were less variable in the more saline layers (S 10) than in the upper brackish and interfacial layers, indicating lower dynamics and less pronounced influence of secondary processes on the inorganic iodine distribution. An increase in iodate and iodide concentrations toward the estuary mouth was determined in the upper layers. Seasonal variations in iodate and iodide distributions in the brackish layer were indicative of the important role of the freshwater phytoplankton and organic matter for the inorganic iodine cycle in the estuary.