Effect Of Marine Bacteria On The Growth And Toxicity Of Alexandium Tamarense

Red-tide is a serious global marine disaster. In the recent years, the apparent global increase inthe occurrence of red-tide has been accompanied with the enlargement of red-tide area and moreharmful to ecological environment and human body. It has been an instant problem that how tomanage and abate or even prevent red-tide efficiently Presently people mainly used chemicalmethod to prevent red-tide, though this method could control red-tide rapidly and efficiently, itwould bring new contamination to marine environment. Marine bacteria play a great role in theoccurrence and declination of red-tide based on their population diversity biophysiological andbiochemical character diversity, ecological function diversity and heredity diversity Thus,bacteria-alga relationship has been a hotspot in red-tide research.For the first time, we studied the effect of marine bacteria, isolated from Xiamen West SeaArea, on the growth and toxicity of Alexandrium tamarense under lab condition. The results wereas follows:1. Nine strains of marine bacteria were isolated from sediment of Xiamen West Sea Area. Threeof them were chosen for the next experiment after preparatory experiment.2. The toxicity of this strain of A.tamarense was about (0.95~12.14 ) × 106 Mu/cell. The resultsshowed that the toxicity per cell reached the peak value at the metaphase of growth logphase(12-14d) and decreased later.3. Different stains of marine bacteria and different concentration of same bacteria strain haddifferent effects on the growth and toxicity of A.tamarense① The growth of A.tamarense was inhibited obvious1y by the strain S10 at a highconcentration (6.34 × 1010. 6.34 × 108 cells/ml), but at a low concentration (6.34× 106 cells/ml) it has no evident effect on the growth of A.tamarense. The PSPproduction of A.tamarense was also inhibited by S10 at different concentration3especiaIIy at low concentration (6.34 X I0' cells/ml ).@ The function of the strain P42 was contrary to the strain SIo' The groWth ofA.tamarense was inhibited obviously by the strain P42 at a high concentration (6.34 Xl0s. 6.34 X l0e cells/ml ), The PSP production of A.tamarense was inhibited by P42 atdifferent concentrations, especially at high concentration (6.34 X l0,o celIs/ml).@ The effects of both strain P44 and P54 on the groWth and toxicity of A.tamarense wasmore weaker than those of strain SIo and P42. The PSP production of A.tamarense wasinhibited lightly by P44 and P54 only at the beginning of groWth log phase, then theeffect weakened at the anaphase.4. The effects of Slo on the groWth and toxicity of A.tamarense under different pH and differentsalinities were studied, the result showed that f@ The alga grew wel1 at pH6~8, and a salinity of 20%,~34%,.@ The toxicity of A.tamarense varied markedly under different pH and saIinity Thetoxicity decreased when the pH increased, whilist it increased with salinity and reachpeak value at the salinity of 30%,, then it declined.@ The strain Slo inhibited the groWth and the PSP production of A.tamarense at differentpHs and salinities except at pH 6, which promoted the groWth of alga instead. Thestrain SIo had the best inhibitory function on the growth of A.Iamarmse at pH 7 and asaIinity of 34ki. The best inhibitory function on the PSP production of A.otarensewas at pH 7, but this inhibitory function on the PSP production did not relatCd tosaIinity.