Characterization of Intracellular Iodine Accumulation by Iodine-Tolerant Microalgae

High iodine concentrations are thought to be toxic to algal growth. However, in this study, among tested 10 algae, 6 species (Bellerochea sp., Chlamydomonas reinhardtii, Dunaliella tertiolecta, Isochrysis galbana, Skeletonema costatum, Tetraselmis sp.) exhibited high iodine tolerance and 2 species showed positive growth responses (Emiliania huxleyi, Gephyrocapsa oceanica). On the other hand, growth of Chlorella kessleri and Chaetoceros sociale were strongly inhibited. Interestingly, the effect of iodine differed among algal species and between the molecular forms of iodine, namely iodide (I−) or iodate (IO3−) ions. Neutron activation analysis indicates that E. huxleyi intracellularly accumulated more iodine when grown in KIO3 than when grown in KI. Such high intracellular iodine accumulation may stimulate the growth. Moreover, E. huxleyi accumulated ca.10 times more iodine than that found in seawater, suggesting that microalgae can be used in iodine-related industries for extracting iodine from seawater and iodine-containing wastewater.