Study on impact of dinoflagellate Alexandrium tamarense on life activities of marine bivalves

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