The effects of a PSP producing dinoflagellate Ale xandrium tamarense on marine bivalvesat their several important life stages: egg, D- shape larva, eyespot larva, juvenile and adult, were stud-ied. The results show that the hatching, survival, activity, filtration and growth were adversely affectedby the alga and the impact was significantly increased with the increase of algal density. The inhibitoryeffect on egg hatching was most significant, which the hatching rate was only 30% of the control whenexposed to the alga at 100 cell/cm3 after 36 h. Further experiments show that the algal culture, re-sus-pended cells and cell fragments had the inhibitory effect, while no such effect was from the cell-freemedium, cell contents and standard STX. The results indicate that the alga could produce unknown tox-ins, rather than PSP, associated with the cell surface.
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