| In the last few years, Dinoflagellates blooms occur frequently and it is imperative to seek more applicable control strategies to prevent the occurrence and mitigate the harmful effects of Dinoflagellates blooms. The present dissertation aims to study the toxicity, motility and growth inhibitory activity of the three kinds of surfactants with the advantages of low toxicity, high biodegradability and ecological acceptability. The motility and growth inhibitory effects of rhamnolipid biosurfactant, APG (A) and APG-131 on some common Dinoflagellates were studied; the removal efficiencies of rhamnolipid-clay combination on these Dinoflagellates were also studied; The toxicities of the three kinds of surfactants were examined in order to apply reference for the effect of the three kinds of surfactants on the ecological environment. In the experiment Heitou fish was used as the representative mariculture. A train of study results are obtained which can definitely provide valuable scientific evidence, theoretical foundation and experimental basis for the prevention and control of Dinoflagellates blooms.â… . The motility and growth inhibitory effects of the three kinds of surfactants on some common Dinoflagellates were investigated, the mechanism of the different motility and growth inhibitory activity of the three kinds of surfactants on the Dinoflagellates were also studied.1. When the concentration of rhamnolipid arrived at 5mg/L, the motility inhibition of P.donghaiense, Gymnodinium sp, S.trochoidea, A.tamarense and P. marinum all nearly reached 100% during 30min; When the concentration of APG (A) arrived at 4mg/L, 8mg/L and 6mg/L, the motility inhibition of P.donghaiense, Gymnodinium sp and P. marinum all reached 100% during 30min; When the concentration of APG-131 arrived at 2mg/L, the motility inhibition of P.donghaiense, Gymnodinium sp and S. trochoidea reached 90% during 30min. In addition, when the concentration of rhamnolipid arrived at 5mg/L, the motility inhibition of P.minium reached above 80% during 30min; When the concentration of APG (A) reached 4mg/L, the motility inhibition of S.trochoidea and A.tamarense reached above 80% during 30min; when the concentration of APG-131 arrived at 2mg/L, the motility inhibition of A.tamarense and P.marinum were both less than 80% during 30min.2. When the concentration of rhamnolipid arrived at 4mg/L, 7mg/L and 10mg/L , the growth of P.minium, S.trochoidea and A.tamarense was inhibited completely; When the concentration of APG (A) arrived at 4.5mg/L and 6.5mg/L, the growth of S.trochoidea and P.marinum was inhibited completely; When the concentration of APG-131 arrived at 3mg/L, 0.6mg/L and 0.8mg/L, the growth of Gymnodinium sp, S.trochoidea and P.marinum was inhibited completely. In addition, the growth of P.marinum in the presence of rhmnolipid and the growth of Gymnodinium sp and S.trochoidea in the presence of APG (A) were also inhibited obviously.3. The motility and growth inhibitions of the three kinds of surfactants on the Dinoflagellates were different. To different genus, it may relate to appendant structure of surface, inner composition and individual size of the Dinoflagellates cells. To the same genus, it may relate to the fatty acid composition, especially the proportion of polyunsaturated fatty acids (PUFAs) of the biological membranes of the Dinoflagellates. Namely, the motility and growth of inhibitory effect of surfactants on the algae increases with the decreasing proportion of PUFAs of the algae.â…¡. The toxicity experiment was conducted to confirm the safety concentrations of the three kinds of surfactants to Heitou fish. The result can apply reference for the effect of the three kinds of surfactants on the ecological environment. â‘ The safety concentrations of APG (A) and APG-131 were 1.25mg/L and 0.25mg/L by the pre-toxicity experiment results, the results proved that the two kinds of surfactants may influence the mariculture when it was used in removing red tide organism.â‘¡The safety concentration of rhamnolipid was 7.28mg/L, 5mg/L rhamnolipid was used in the rhamnolipid-clay combination. So this kind of biosurfactant would not evidently influence the mariculture when it was used in removing red tide organism.â…¢. The removal efficiencies of rhamnolipid-clay combination on Dinoflagellates were investigated, the mechanism of the different removal efficiencies of rhamnolipid-clay combinations on the Dinoflagellates was also studied.Through the thorough simulation experiments, it was concluded that when the combination was 5mg/L rhmnolipid and 1g/L clay, the removal efficiencies of P.donghaiense, Gymnodinium SP, S.trochoidea, A.tamarense and P.marinum separately reached 89.13%, 84.09%, 68.42%, 95.50% and 47.37%. They are much higer than the efficienes of rhamnolipid which were only 69.53%,-3.53%,66.55%,84.35% and -21.14%, and the efficiencies of clay which were only 22.66%,2.35%,-16.64%,-6.25% and -7.4% , the average increase were 37.75 % and 7.96 %, Equivalent to decrease rhamnolipid 1.37 mg/L and clay 0.44 mg/L.
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