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 w ith a specic toxicity of( 93. 42 ± 2. 55) × 10- 6MU / cell w as fed in this w ork. Firstly,the effect in clearance rate of A. minutum at 6 different concentrations of 0. 5 × 103-3. 0 × 103cells / mL w as discussed. Then the concentration of 1. 5 × 103cells / mL of toxic algae w as fed,and the accumulation of the 15 h short-term and 5 days long-term accumulation experiments w ere conducted to study the toxicity and accumulation law s,respectively. Results show ed the oyster clearance rate is higher betw een concentrations 0. 5 × 103- 1. 5 × 103cells / mL,but w hile more than 1. 5 × 103cells / mL,it fell significantly( P 0. 01),indicating that the "threshold"toxic algae concentration w as 1. 5 × 103cells / mL. The oyster finished food that w as offered once during the 0- 6 h experiment,the maximum toxicity of oyster w as( 149. 6 ± 10. 5) MU /100 g during 6- 12 h and then began to decline. When fed oysters tw ice daily w ith concentration of A. minutum( 1. 5 × 103cells / 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 follow ing day. At the end of the accumulation experiment,PSP toxin level w as as high as( 3 069. 2 ± 178. 2) MU /100 g,w hich w as 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.