SHELL GROWTH-RESPONSE OF MUSSELS (MYTILUS-EDULIS) EXPOSED TO TOXIC MICROALGAE

Mussels (Mytilus edulis) were exposed to the algae Alexandrium ostenfeldii, Chrysochromulina polylepis, Gyrodinium aureolum, Gymnodinium galatheanum and Heterosigma akashiwo for 24 h; significant reductions in growth rate, as compared to the control, were observed after exposure to A. ostenfeldii, C. polylepis, G. aureolum and G. galatheanum at initial concentrations of 4.5 x 10(6), 110 x 10(6), 9 x 10(6) and 120 x 10(6) cells l-1, respectively. Exposure to high initial concentrations of the non-toxic algae Tetraselmis suecica (174 x 10(6) cells l-1) and Isochrysis galbana (610 x 10(6) cells l-1) showed no adverse effect on growth rate. When mussels with reduced growth were transferred to clean seawater, they recovered to > 90% of control growth within 2 to 4 d. Exposure to algal filtrates of the toxic algal cultures produced no reduction in growth rate.