Preliminary Study On The Toxicity Of Non-PSP-producing Alexandrium Affine

The toxicity of a non-PSP producer of the dinoflagellate Alexandrium affine (AC-1) was investigated in this paper. Its acute effects on Brachionus plicatilus, Artemia salina and Neomysis awatschensis and the chronic effects on N. awatschensis were studied. The components analysis of AFT toxins produced by the alga was also examined. The results were shown as following:The acute effects on B. plicatilus, A. salina and N. awatschensis by non-PSP-produced A. affine were studied. The results showed that A. affine could affect the survival of B. plicatilus, A. salina and N. awatschensis. 96hLC50 of B. plicatilus, A. salina and N. awatschensis were 1500cells/ml, 90cells/ml, and 5000cells/ml, respectively. The toxicity comparison of A. affine on B. plicatilus, A. salina and N. awatschensis indicated that A. salina was more obviously affected by A. affine than B. plicatilus and N. awatschensis.The effects of A. affine on growth and reproduction on N. awatschensis were influenced significantly. Chronic experiment (63days) showed that the reproduction of N. awatschensis was obviously affected at 50cells/ml A. affine. At the end of the experiment, the highest number of juveniles per day, the total numbers of juveniles produced and the total releasing days were reduced, and the first releasing time was delayed, as well as reproduction break of the parent mysids were increased, when exposed to the algae. It was also found that A. affine could affect the survival and growth of the parent mysid: in 50cells/ml A. affine, the survival rate of N. awatschensis was 71%. The length and weight of adult shrimps were 87.3% and 97.8% respectively, but the difference was not significant (P>0.05). The toxicity of different fractions (algal culture, re-suspended cells, free-cell medium, and cell contents) of A. affine was studied. The results showed that the algal culture and re-suspended algal cells all had strong impact on B. plicatilus, A. salina and N. awatschensis. It indicated that the toxicity of A. affine was mostly related with the living algal cells. The free-cell medium and cell contents had also the adverse impact on B. plicatilus, A. salina and N. awatschensis, but it was not significant on N. awatschensis. The results implied that AFT toxins might originate from the cell inner and could secrete to the cell culture medium.The basic components analysis of AFT toxins including the thermal stability, acid and alkali stability, molecular weight, the toxicity of non-proteide component, polarity of AFT toxins produced by A. affine were studied. The results showed that the toxicity of AFT toxins was not magnificently affected by temperature and pH. Their molecular weight was estimated to be 5k to 50k. And they were determined as polysaccharide substances by the absorption spectrum scanning and Molicsh test.The above results showed that A. affine could not produce PSP toxins, but it could produce polysaccharide toxins which had adverse influence on population and resources of crustacean zooplankton. This can help us further explore the harmful mechanism and structure of AFT toxins. It also can help us better understand harmful impacts of Alexandrium spp.