Study On Fast And Sensitive Method And Mechanism Controlling The Growth Of Red Tide Algae

Object: The removal effects of some chemicals on red tide algae, Phaeoecystis globosa and Alexandrium tamarense, were observed to screen sensitive, fast and highly efficient algaecides in controlling red tide.The removal mechanism of the algaecide screened was discussed.Method: Chlorine dioxide (oxidant), biquaternary ammonium salt (surfactant) and tertbutyl triazine(photosynthesis inhibitor), etc. were used to remove Phaeoecystis globosa or Alexandrium tamarens at different cell density. The results showed that the three chemicals could effectively control the growth of Phaeoecystis globosa or/and Alexandrium tamarens in 96 h. On the basis of comparation in removal efficiency and toxicity, etc. of the chemicals, the effect of chlorine dioxide, the best candidate to control red tide, on chlorophyll a, protein, amino acid and nucleic acid of Phaeoecystis globosa was studied.Meanwhile, the change in cell morphology induced by chlorine dioxide was observed by electron microscope.Result: When the density of algae of Phaeoecystis globosa was 2.35 109, 1.18 109, 4.70 108, 1.18 108 cells-L-1, the concentration of chlorine dioxide which could kill the algae efficiently in 96 h was respectively 2, 1.5, 1, 0.4 mg-L-1.That is , at the same rate of inhibition or elimination, the higher the density of algae was, the lower the concentration of chlorine dioxide to control effectively the algae was. The efficient concentration of biquaternary ammonium salt to control Phaeoecystis globosa (5.8 108 cells-L-1) and Alexandrium tamarens ( 7.0 106 cells-L-1) in 96 h was 0.8 mg-L-1 and 0.4 mg-L-1, respectively.Tertbutyl triazine to control Phaeoecystis globosa (1.24 109cell-L-1) and Alexandrium tamarens (7.0 106 cells-L-1) in 96 h was 0.6mgL-1 and 0.2 mgL-1, respectively. Taking account of the toxicity, cost and efficiency in controling algae of the three chemicals, they could be considered as a potential algaecide to control red tide, but chlorine dioxide was the best candidate. Chlorine dioxide not only affected the chlorophyll a, the protein, amino acid and nucleic acid of Phaeoecystis globosa, but also damaged cell membrane structure, andcaused important biological substances to leak out of cells.