| In recent years, harmful algal blooms have frequently occurred, which has seriously impact on marine ecosystem and edgangered fishery production and human health. Biological methods especially algicidal bacteria are of particular interest. This study was about the algicidal activity of algicidal substance, the changes of water quality index and N,P concentration in the simulative water. The effect of algicidal substance on marine organisms and Phaeocystis globosa(P. globosa) algal toxin were also studied. The results are followed:(1) The algicidal characteristic of algicidal substance was detected in simulative water,the changes of water quality parameters were determined during the test. Results showed that after adding the algicidal substance at a concentration of 1%(v/v) for 14 d, comparing with control group, in the treatment group, p H was reduced to 7.51 from 8.50, chlorophyll-a and permanganate index were reduced by 82.34%(P<0.05) and 55.19%(P<0.01), respectively.Dissolved oxygen was increased by 29.45%(P<0.05). The concentrations of NH4+-N, NO2--N,NO3--N, TN and PO43--P, TP were respectively 0.5, 1.5, 6.2, 14.8 and 1.3, 0.9 times higher than that in control group. Results showed that the algicidal substance can inhibit the growth of P.globosa(algicidal rate was 82.34%) in the simulative water. Otherwise, water qualities can be affected by algicidal substance.(2) The toxicity of algicidal substances on marine organisms was tested by algal inhibition and acute toxicity experiment. Results showed that after exposure to the algicidal substance at a concentration of 1.0(v/v) for 96 h, there was no toxic effect on Chlorella vulgaris,Chaetoceros mulleri and Isochrysis galbana. The 24 h LC50 values for Moina mongolica Daday,Brachionus plicatilis, Artemia salina were 15.4 1, 8.49 and 1.30 %(v/v), 48 h LC50 values were9.00, 5.66 and 1.02%(v/v), respectively. The 24, 28, 72, 96 h LC50 values for goldfish were 14.35,12.07, 10.46 and 9.06%(v/v), respectively. Results indicated that at the concentration of1.0%(v/v) which can inhibit P. globosa effectively, algicidal substance had no toxicity on marine organisms. The algicidal substace can be considered as ecologically and environmentally biological agents to control harmful algae.(3) The hemolysis activitives of P. globosa intracellular algal toxin were 81.2, 31.8, 20.1,19.3 and 21.3% after 5 d when the concentration of algicidal substance was 0, 0.5, 1.0, 1.5 and2.0%(v/v), respectively. These results indicated that algicidal substance not only can inhibit the growth of P. globosa, but also reduce the hemolysis activity of P. globosa intracellular algal toxin.(3) After the growth of P. globosa was inhibited by algicidal substance, the compositions of algal toxin and fatty acids were detected by HPLC and GC-MS. Results showed after adding1.0%(v/v) algicidal substance for 5 d, the algal toxin of P. globosa in treatment group contained7 compositions, while there were 8 compositions in control group.The concentration of total fatty acid was reduced by 83.4%. The major fatty acids C18:2, C16:0 and C18:1were reduced by 100, 97.7and 85.4%(P<0.01), respectively. These results indicated that the toxicity of P. globosa was decreased, the concentration of algal toxin was also decreased as the addition of algicidal substance. |
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