Growth Characteristics And Toxin Determination Of Four Species Of Pseudo-nitzschia From Southeast China Sea

This dissertation mainly focuses on the studies on four species of genus Pseudo-nitzschia isolated from Southeast China Sea and the studies include the morphological study, growth study underd different conditions, toxin (Domic Acid) determination and the primary exploration of the reasons why the Pseudo-niztschia distributed in China Sea cannot produce DA. The morphological study, growth and toxin (Domic Acid) determination on the six strains of P. multiseries (from Canada) were also carried out. The different DA yields between the P. multiseries strains and different cell cycle are analyzed. In addition, the toxin (Domic Acid) determination were also carried out on thirteen pennate species (twenty-one strains) isolated from China coastal sea area and the possible reasons of the toxin in seashells were discussed. The results are as followed:Thirteen strains of Pseudo-nitzaschia isolated from different locations in Southeast China Sea by microtube method. These thirteen strains Pseudo-nitzschia, are identified as four species that are P. pungens, P. multiserita, P. cuspidata and P. brasiliana by light microscope and electron microscope. Except the P. brasiliana, the rest have been reported to be toxin producers.Taking the cell density, Chla and growth rate as the indicators, four species of Pseudo-nitzschia that are isolated from different locations of Southeast China Sea were studied by being cultivated respectively under normal conditions and different inducing conditions. The results suggested that the strains isolated from different locations have differences in growing conditions under the normal cultivating conditions, which supported that the same species from different geographical areas do have differences. And as for the same species, the differences do exist under the different cultivating conditions, which showed that the changes of environmental factors can influence the growth characteristics.Deficiency of silica and phosphorus, different photoperiods were set as the inducing cultivation. According to the HPLC measurement, no DA was determined under the set cultivating conditions, which lead to the conclusion that these four species of Pseudo-nitzschia under the study cannot produce DA either under the normal conditions or inducing conditions.Under the normal conditions, the growth study between the strains, the toxin (Domic Acid) determination and DA yield analysis were also carried out on the P. multiseries provided by the Bates Steven, (Bedford institution of oceanography, Canada). The results approve the testing method applied in this study is feasible and accurate. And what is more, the result provide the rudimentary data for further study on the comparison between the DA producers and no DA producers, and the laid the foundation for exploration of the reasons why the Pseudo-niztschia distributed in China Sea area cannot produce DA.DA-HPLC was also carried out on 21 strains which belong to 13 species of pennate diatoms isolated from China Sea. The results showed that 21 species of pennate diatoms cannot produce tested DA.