Effects of Ozonation on the Speciation of Dissolved Iodine in Artificial Seawater

Abstract

Iodine in the form of iodide is required for synthesis of tri-iodothyronine and thyroxine in fish. Iodine chemical speciation in aliquots of raw artificial seawater mix was measured before, during, and after exposure for fixed time periods to air only and to concentrations of ozone required to achieve oxidation-reduction potentials typical of a protein skimmer (400 mV) and an ozone contact chamber (800 mV). Chemical species of iodine were also measured in tank water from a large, recirculating, ozonated aquarium system that has a low-grade incidence of thyroid lesions (e.g., thyroiditis, hyperplasia, adenoma, and adenocarcinoma) in its fish. With increasing exposure to ozone, concentrations of iodide and dissolved organic iodine (DOI) decreased, whereas iodate levels increased. As a result of exposure to 400 mV, iodide concentration dropped to less than half the amount found in raw artificial seawater mix. After exposure to 800 mV, initial iodide levels decreased by 67%, and DOI became undetectable, whereas iodate concentration increased by 155%, with no remarkable change in total iodine concentration. These results indicate ozone-induced conversions from iodide to iodate, and DOI to iodide or iodate (or both). Iodide and DOI were not detectable in the aquarium system's water samples. Ozonation of artificial seawater may alter the relative concentrations of iodine species in a closed tank system, so that iodide supplementation of the diet or tank water of captive teleosts and elasmobranchs living in ozonated seawater is advisable.

Iodine nutrition and toxicity in Atlantic cod (Gadus morhua) larvae

“…Nitrate (NO 3 − ) is goitrogenic as it competitively blocks iodide uptake by the sodium iodide symporter (Tonacchera et al, 2004), and NO 3 − at levels commonly found in recirculation systems causes goitre in sharks (Crow et al, 1998; Morris et al, 2011). Furthermore, ozone (O 3 ) used as a disinfectant in recirculation systems readily oxidises bioavailable I, iodide (I − ) to iodate (IO 3 − ) (Sherrill, Whitaker & Wong, 2004). Dissolved iodate is presumed to have low bioavailablity for fish (Sherrill, Whitaker & Wong, 2004), and higher levels of iodate compared to iodide were correlated to poor growth and survival in well water reared pacific threadfin larvae (Witt et al, 2009).…”

Iodine and selenium supplementation increased survival and changed thyroid hormone status in Senegalese sole (Solea senegalensis) larvae reared in a recirculation system

“…It is known that iodine deficiency can create hypothyroidism and goitre in fish (Leatherland 1994;Moccia et al 1981;Sonstegard and Leatherland 1976). Moreover, it has been shown that fish reared in well water with low levels of iodine or in aquaria, with a recirculation system and an ozone contact chamber, can develop goitre (Sherrill et al 2004;Witt et al 2009). Ozone contact chambers have a powerful oxidation-reduction potential (Sherrill et al 2004), altering the water concentration of iodide (I -) by converting it into iodate (IO 3 -) (Bichsel and von Gunten 1999;Sherrill et al 2004).…”

“…Moreover, it has been shown that fish reared in well water with low levels of iodine or in aquaria, with a recirculation system and an ozone contact chamber, can develop goitre (Sherrill et al 2004;Witt et al 2009). Ozone contact chambers have a powerful oxidation-reduction potential (Sherrill et al 2004), altering the water concentration of iodide (I -) by converting it into iodate (IO 3 -) (Bichsel and von Gunten 1999;Sherrill et al 2004). Fish reared in iodide-depleted water, fed diets low or deficient in iodine may develop thyroid hyperplasia (Sherrill et al 2004), but when the larvae were fed extra iodine through their diet, the follicles developed normally (Ribeiro et al 2009).…”

“…Ozone contact chambers have a powerful oxidation-reduction potential (Sherrill et al 2004), altering the water concentration of iodide (I -) by converting it into iodate (IO 3 -) (Bichsel and von Gunten 1999;Sherrill et al 2004). Fish reared in iodide-depleted water, fed diets low or deficient in iodine may develop thyroid hyperplasia (Sherrill et al 2004), but when the larvae were fed extra iodine through their diet, the follicles developed normally (Ribeiro et al 2009). Ribeiro et al (2009) found that Senegalese sole larvae developed hyperplasia and goitre when reared in a recirculation system with ozone injection.…”

Iodine enrichment of rainbow trout flesh by dietary supplementation with the red seaweed Gracilaria vermiculophylla

“…Iodine deficiency leads to the appearance of hypothyroidism and goiter in vertebrates, including fish (Lall, 2002;Leatherland, 1994;Ribeiro et al, 2012). According to NRC (2011) the requirement of salmonids for dietary iodine is relatively low (1.1 mg/kg), but iodine deficiency might still occur in freshwater systems with low iodine content or in closed tank systems where ozonation of artificial seawater may alter the relative concentrations of iodine species (Ribeiro et al, 2012;Sherrill et al, 2004). Iodine deficiency disorders (IDD) are described in many geographic areas due to iodine scarcity.…”