Effects of the dinoflagellate Alexandrium tamarense on early development of the scallop Argopecten irradians concentricus

The effects of Alexandrium tamarense (strain ATHK) on early development of the bay scallop Argopecten irradians concentricus were studied under laboratory conditions. The algal culture was verified by HPLC to produce paralytic shellfish poisoning (PSP) at a level of 37.48 fmol/cell. Survival of the scallop larvae was not affected when they were grown with A. tamarense at concentrations of 500-10,000 cells/ml for 48 h. However, the activity of D-shape larvae was inhibited after 48-h exposure to A. tamarense at the algal cell density of 10,000 cells/ml. Scallop growth was inhibited significantly by A. tantarense during a 14-day exposure starting at the eye-spot larval stage. The size of juvenile scallops in the group of 10,000 cells/ml was only about 32% of that of the controls, although no obvious effect of A. tamarense was found on the rate of larval metamorphosis. All juvenile scallops survived in algal concentrations of 600-2400 cells/ml, however, attachment rates were significantly lower than control values after a 5-h exposure to A. tamarense at concentrations >600 cells/ml, while they were not obviously reduced after only 1 h of exposure. At concentrations >600 cells/ml, the climbing ability of juveniles was clearly reduced by exposure to A. tamarense after only 1 h. The climbing rate and height were only 55% and 45%, respectively, of those of the controls, when exposed to A. tantarense at a concentration of 600 cells/ml. The results indicated that A. tamarense blooms may have detrimental impacts on shellfish at early life stages, therefore, special attention should be paid to the toxic algal blooms in shellfish breeding area. (C) 2003 Elsevier Science B.V. All rights reserved.