Effect Of Environment And Nutrition Factors On The Growth And Hemolytic Activity Of Aureococcus Anophagefferens

In the summer of 1985,the brown tide caused by Aureococcus anophagefferens was firstly recorded on the northeastern coast of the United States and the mid-Atlantic coast of Narragansett Bay and Rhode Island.Since then,blooms of A.anophagefferens have plagued in the incident and adjacent sea areas.These continuous,high frequency and large area blooms had resulted in a devastating blow to local sea environment and mariculture.In this paper,effect of environment conditions of light intensity,temperature,salinity and trace elements on growth and hemolytic activity of A.anophagefferens(Qinhuangdao strain)was studied.Effect of different environmental conditions on its chlorophyll fluorescence characteristics was also studied to reveal the relationship between photosynthesis and hemolytic activity of A.anophagefferens.We further inverstigated the changes of fatty acid content and hemolytic activity of A.anophagefferens under the conditions of nitrogen-deficient,phosphorus-deficient and iron deficient to reveal the relationship between fatty acid and hemolytic activity of A.anophagefferens.The results were as follow:Low light intensity had a significant positive effect on the growth and hemolytic activity of A.anophagefferens.In the light conditions of 180?mol·m-2·s-1,decline phase of A.anophagefferens was earlier than the other light intensity.In the light intensity ranged from 60 to 180?mol·m-2·s-1,hemolytic activity per unit volume and unit cell of A.anophagefferens in the high light was about half as long as in the low light.It was suggested that low light intensity promoted the growth and hemolytic activity of A.anophagefferens.A.anophagefferens was able to grow at the temperatures ranged from 15 to 25?.The maximum cell density was abtained at the temperature of 20?.However,there was no significant effect on the hemolytic activity of A.anophagefferens in these culture temperatures.In the range of salinity 20~40,the algae showed different degrees of growth.The optimal growth salinity of A.anophagefferens were 25~35.It was showed that hemolytic activity per unit volume and unit cell of A.anophagefferens cultured in the salinity of 30~35 were significantly higher than that of other salinity groups.The growth and hemolytic activity of A.anophagefferens were consistent with the regulation of temperature,salinity and light intensity.It was also showed that the hemolytic activity of A.anophagefferens was enhanced under the optimal growth conditions.Copper ion concentration had a significant effect on growth and hemolytic activity per unit volume of A.anophagefferens.The cell density of A.anophagefferens and hemolytic acitivity reached the maximum at a Cu2+ concentration of1× 10-8 mol·L-1.A low Cu2+ concentrations inhibited the growth of A.anophagefferens and a higher Cu2+ concentration promoted the growth.Hemolytic activity per unit volume of A.anophagefferens reached the highest when A.anophagefferens was cultured in the copper ions of 1×10-8 mol·L-1.However,there was no difference in hemolytic activity per unit cells,indicating the consistency of growth and hemolytic activity.A.anophagefferens has a wide adaptability to iron ions,the cell grew well in iron-deficient medium.A.anophagefferens grew well in the medium of 0~1×10-5 mol·L-1 iron ion concentration,and maintain a consistent growth cycle and maximum cell density.Although the growth of A.anophagefferens was not affected by iron ions,hemolytic activity per unit volume was increased at the high concentrations of iron ions.There was a significant difference in the hemolytic activity per unit volume,and there was no significant difference in the hemolytic activity per unit cell.A.anophagefferens could grow in the concentration of manganese ions from 1×10-10 mol·L-1 to1× 10-6 mol·L-1.Hemolytic activity of A.anophagefferens was significantly different under different manganese ion concentrations.The high concentration of manganese ion promoted the synthesis of hemolytic toxins of A.anophagefferens.Eight unsaturated fatty acids was found in A.anophagefferens,which were dominated by stearidonic acid,docosahexaenoic acid(DHA),linolenic acid and eicosapentaenoic acid(EPA).Iron and phosphorus limitation reduced the content of eicosapentaenoic acid(EPA),but did not affect hemolytic activity of unit cells,indicating that EPA may not be related to the hemolytic activity of A.anophagefferens.The photosynthetic fluorescence parameters Fv/Fm,Yield and ETR values of A.anophagefferens were significant effected by the light intensity.In the range of 60~180?mol·m-2·s-1,the photosynthesis rate and hemolytic activity of A.anophagefferens were enhanced by low light intensity.No different values of Fv/Fm,Yield and ETR of A.anophagefferens was found when the cell cultured at the temperature ranged from of 15 to 25?.It was indicated that the photosynthetic rate was not significant effected by temperature.Salinity ranged from 20 to 40 significantly affect the Fv/Fm,Yield and ETR values of A.anophagefferens.High salinity inhibied photosynthetic efficiency of A.anophagefferens.By comparing chlorophyll fluorescence parameters with hemolytic activity,the results showed that hemolytic activity of A.anophagefferens was consistent with photosynthesis potential and efficiency.Above all,A.anophagefferens has a wide adaptability to light intensity,salinity,temperature and trace metal elements.Compared with other harmful algae,A.anophagefferens grow better with low temperature,low light intensity and high salinity and trace metal elements(iron,copper and manganese ions).Under the optimal growth conditions,A.anophagefferens usually has the highest photosynthetic potential and efficiency.Hemolytic activity per unit volume or unit cell was also enhanced under the optimal growth conditions.