Abstract:The toxicities of the alga of Phaeocystis globosa and the red tide seawater collected from the seaport in Zhanjiang City in April 2005, were detected. The dispersed alga colony had certain impact on the survival of young Penaeus vannamei Boone shrimps with 24 h LC50=1.0×109 cells L-1. The mortality of the young shrimps was as low as 10% exposed for 24 h to 1.00×109 cells L-1 of the alga colony removed of liquor. The red tide seawater had toxicity neither against the young shrimps nor against Epinephelus awoara （3 mm） fry. P. globosa exhibited no toxicity against the fry of Mugil cephalus and Latescal carifer. E. awoara fly were, however, sensitive to the alga, of which half died within 24 h in the presence of the alga colony liquor accounting for 10.9% of seawater volume．
