The Ecotoxicity Of Dinoflagellate Alexandrium Tamarense On Mysid Neomysis Awatschensis And Perch Lateolabrax Japonicus

The effect of the dinoflagellate Alexandrium tamarense(ATHK) on the survival, growth and reproduction on Mysid Neomysis awatschensis and the acute effects on juvenile Perch, Lateolabrax japonicus, as well as the toxicity of different fractions of the algal culture on Perch were studied. The ingesting and PSP accumulating experiment were carried out to know the transfer of PSP in these food -chain. Using bioassay of A. salina, mouse and N. awatschensis, toxicity of a HAB event in JiaoZhou Bay in July 2000 was evaluated.The results showed: A. tamarense could affect the survival, growth and reproduction of N. awatschensis, and the effects increased with the algal concentration. In acute experiment, the mortality rate in 9,000 cells·ml-1 A. tamarense was 55%, over 10% shrimps died in 900cells·ml-1 A. tamarense, and 96hLC50 of N. awatschensis was 7,000cells·ml－1. There were 25% N. awatschensis which died in the cell-free filtrate after 96 hour exposure. The acute results also showed that the cell-free filtrate of A. tamarense could effect survival rate of N. awatschensis significantly in a short time. Chronic experiment (62days) showed that A. tamarense could affect the total juvenile population of N. awatschensis. The total numbers of juveniles produced were only 106, 32 and 27 in algal concentrations of 90, 450, 900 cells·ml－1, respectively, while 164 juveniles were released in the control group during the same period. The first releasing time, total releasing days, reproduction break of the parent mysids and the highest number of juveniles per day were also influenced significantly by this toxic dinoflagellate. In concentration of 900 cells·ml－1, the first releasing day was prolongedfor 3 days compared with that of the control; the total releasing days was 9, while it was 28 in control; the adult shrimps had 3 reproductive breaks during the reproduction period. The highest number of juveniles produced per day was 7 at this concentration, while it was 17 in control. It was also found that A. tamarense can affect the survival and growth of the adult mysid: in 900cells·ml－1 A. tamarense, the mortality rate of N. awatschensis was 37%. The length and weight of adult shrimps were 95.6% and 81.9% respectively of those of the control, but the difference was not significant (P>0.05).Culture of dinoflagellate A.tamarense showed obvious impact on the survival of the juvenile Perch(2.5cm), Lateolabrax japonicus with 96hLC50= 4,000 cells·ml－1. The toxicity of different fractions of the algal culture (equivalent to 8,000 cells·ml－1):re-suspended cells,cell-free medium,cell contents and cell fragments were compared. The re-suspended cells showed similar strong impact as the culture on the survival of the juvenile fish, and the cell content also resulted in significantly such adverse effect, however, the other fractions did not produce any obvious toxicity. The results indicated that PSP toxins ingestion may be the lethal factor to the juvenile fish mortality. The experiment also found that the young fish(12cm)was not sensitive to the toxic alga,and could survive during the exposure to algal cells at 10,000 cells·ml－1 for ten days.The results of ingesting experiment showed that A. salina and N. awatschensis can ingest A. tamarense, but the ingesting ability on A. tamarense of A. salina exceeds that of N. awatschensis. And the content of chlorophyll-a of A. tamarense in A. salina and N. awatschensis was 0.87 and 0.024μg·mg-1, respectively. The prior results showed L. japonicus could also ingest A. tamarense. Therefore, A. salina, N. awatschensis and L. japonicus could ingest A. tamarense directly. The A. salina could accumulate the PSP and the PSP content in the sample accumulating for 1, 4 and 5 days all were over 2.0 Mu·g-1. Although the mouse did't die, the sample of N. awatschensis and L. japonicus also made the mouse abnormal as the PSP did. So the PSP can be transferred to Mysid and Perch indirectly..Using bioassay of A. salina, mouse and N. awatschensis , toxicity of a HAB event...