Accumulation of Paralytic Shellfish Toxins (PST) from the Cyanobacterium Aphanizomenon Issatschenkoi by the Cladoceran Daphnia Magna

In order to access the effects of Paralytic Shellfish Toxins (PST) in freshwater environment, the accumulation of PST produced by the cyanobacteria Aphanizomenon issatschenkoi in juvenile Daphnia magna was investigated. D. magna was exposed to A. issatschenkoi cells (1.2 x 10(6) cells ml(-1)) for 6, 8, 12, 24 and 30 h and also to lyophilised material (1 mg ml(-1)) for 24h. Survival and somatic growth of the juvenile D. magna was investigated, as was the activity of the biotransformation enzyme system glutathione-S-transferases (GSTs). Between 643+/-65.35 and 1170+/-51.72 pmol PST ml(-1) were detected by HPLC-FLD in D. magna culture medium containing cells and 2745+/-64.61 pmol PST toxin ml(-1), in the medium containing lyophilised material. PST were detected in D. magna tissues in cells exposure (between 6.51 x 10(-2)+/-1.37 x 10(-2) and 3.78 x 10(-1)+/-1.15 x 10(-2)pmol PST animal(-1)). In D. magna exposed to lyophilised material the mean (+/-SD) PST concentration was found to be 6.96 x 10(-3) (+/-3.84 x 10(-3)) pmol PST animal(-1). Following exposure to 1.2 x 10(6) cells ml(-1)A. issatschenkoi fresh cells growth and survival of D. magna were reduced. D. magna exposed to the two A. issatschenkoi treatments (fresh cells and lyophilised material), showed a reduction in activity of the cytosolic glutathione-S-transferases (cGSTs). The results of this study indicate that D. magna can accumulate PST toxins and that the cyanobacterium A. issatschenkoi affects both the fitness and growth potential of juvenile D. magna.