Tracking a full course from Alexandrium tamarense cysts to mussel toxicity from the eastern coast of Geoje Island, South Korea.

Abstract

A hot spot of the cyst deposition of Alexandrium tamarense (Group I) was searched from the eastern coast of Geoje Island in South Korea. Changes of the cyst abundance and germination ability in the sediment and the vegetative cell abundance and encystment in the water column were intensively monitored at the hot spot. Active germination (ca. 70 %) of the cyst occurred in autumn (Nov. to Dec.). The winter population in lower density (<10 cells L-1) was originated from the germinated cells. The overwintered population initiated the spring bloom and then proliferated to the bloom peak (104 cells L-1) at the moderate temperature (15 ℃) in the middle of April. Decline of the spring bloom was followed by the massive excystment and the increase of predator abundance and feeding activity. 0.046 % of vegetative cell abundances for 85 days in spring were transformed to the encysted cells. Newly encysted cells aestivated during warm summer for next resurrection. Higher feeding rate (ca. 3,000 cells min-1 indiv.-1) of the mussels was measured under the bloom concentration and then resulted in the highest mussel toxicity. and encystment in the water column were intensively monitored at the hot spot. Active germination (ca. 70 %) of the cyst occurred in autumn (Nov. to Dec.). The winter population in lower density (<10 cells L-1) was originated from the germinated cells. The overwintered population initiated the spring bloom and then proliferated to the bloom peak (104 cells L-1) at the moderate temperature (15 ℃) in the middle of April. Decline of the spring bloom was followed by the massive excystment and the increase of predator abundance and feeding activity. 0.046 % of vegetative cell abundances for 85 days in spring were transformed to the encysted cells. Newly encysted cells aestivated during warm summer for next resurrection. Higher feeding rate (ca. 3,000 cells min-1 indiv.-1) of the mussels was measured under the bloom concentration and then resulted in the highest mussel toxicity.