Effects of the toxic dinoflagellate Alexandrium minutum on uptake and the accumulation of PSP toxins in oyster Ostrea rivularis

To study the filter-feeding and accumulation rate of paralytic shellfish poisoning toxins(PSP)in Ostrea rivularts,the strain of A.minutum with a specific toxicity of(93.42±2.55)×10^-6 MU/cell was fed in this work.Firstly,the effect in clearance rate of A.minutum at 6 different concentrations of 0.5×10³-3.0×10³ cells/mL was discussed.Then the concentration of 1.5×10³cells/mL of toxic algae was fed,and the accumulation of the 15 h short-term and 5 days long-term accumulation experiments were conducted to study the toxicity and accumulation laws,respectively.Results showed the oyster clearance rate is higher between concentrations 0.5×10³-1.5×10³ cells/mL,but while more than 1.5×10³ cells/mL,it fell significantly(P<0.01),indicating that the “threshold” toxic algae concentration was 1.5×10³ cells/mL.The oyster finished food that was offered once during the 0-6 h experiment,the maximum toxicity of oyster was (149.6±10.5) MU/100 g during 6-12 h and then began to decline.When fed oysters twice daily with concentration of A.minutum(1.5×10³ cells/mL)up to 5 days,the clearance rate of oyster did not change significantly,it led the toxicity of PSP to exceed the regulatory limit(400 MU/100 g)on the following day.At the end of the accumulation experiment,PSP toxin level was as high as(3 069.2±178.2) MU/100 g,which was higher than the regulatory limit by 7.7 times.Result of the study serve as important basic data of the PSP accumulation and metabolism of Ostrea rivularis,and provide the advanced thinking for the removal and purification of the PSP in fisheries.