Accumulation of iodine into phytoplankton in the coastal region in the North Pacific

Sato, Yuhi; Otosaka, Shigeyoshi  ; Suzuki, Takashi  

Accumulation of iodine into phytoplanktonic organic matter is important process regulating the iodine dynamics in the ocean but it has been poorly understood due to a small number of study examples. To evaluate an accumulation efficiency of iodine by phytoplankton, incubation experiments using cultivated cultures and natural populations obtained from coastal seawater were conducted. The accumulation efficiency of iodine was various in phytoplanktonic species; especially, diatom accumulated iodine significantly per organic carbon. This result suggests that diatom is the key specie regulating the accumulation into phytoplanktonic organic matter in the environment. An iodine/carbon ratio of particulate organic iodine (POI) produced by diatom was estimated, resulting in ca. 410. Multiplying this ratio with net productivity of diatom, an amount of POI produced by phytoplankton in the environment may be roughly estimated.