温度对旋链角毛藻(Chaetoceros curvisetus)和米氏凯伦藻(Karenia mikimotoi)生长及硝酸还原酶活力的影响

Effects of Temperature on The Growth and Nitrate Reductase Activity of Chaetoceros curvisetus and Karenia mikimotoi

选用东海常见的两种赤潮肇事藻种：旋链角毛藻和米氏凯伦藻,采用一次性培养实验,研究了不同温度对两种赤潮藻生长及硝酸还原酶活力（NRA）的影响.研究结果表明,在10℃-30℃条件下旋链角毛藻均能正常生长,且生长曲线均符合S-logistic2种群增长模型;而米氏凯伦藻在10℃和30℃条件下不能正常生长,在其他温度条件下生长情况与旋链角毛藻相似.温度适宜时,两种藻的硝酸还原酶活力最大值（NRAmax）、最大生长速率（μmax）和终止生物量（Bf）随温度的变化趋势基本一致,说明温度的高低可通过影响细胞硝酸还原酶活力大小间接影响藻类的生长.旋链角毛藻单位体积的NRAmax和最大生长速率均大于米氏凯伦藻,说明旋链角毛藻能够更好地吸收利用硝酸盐.

Two dominant microalgae species in the East China Sea （ESC）, Chaetoceros curvisetus（C, curvisetus） and Karenia mikimotoi （K. mikimotoi）, were chosen to study the effects of temperature on microalga growth, nitrate reductase activity （NRA）, and their relationship under laboratory set-up. At the beginning of the incubation, DIN, PO4-P, and SiO3-Si were added to 4 500 ml sea water in 5 L bottles to form a final concentration of 32 μmol/L, 1.5 μmol/L and 32 μmol/L, respectively. The bottles were then incubated under ambient sunlight（about 50 W.m-2） at different temperatures （10℃, 15℃, 20℃, 25℃, and 30℃） for 10-20 days. Triplicates were employed for all treatments. The microalgae cell numbers were counted by hemacytometer counting method. S-logistic 2 population growth model was used to simulate microalgae growth , and calculate two growth-related parameters, the maximum growth rate （μmax） and the final biomass （Bf）. The activity of nitrate reductase was measured in vitro and its relations to microalgal growth were elucidated. The two microalgae were observed to adapt to different temperature ranges. C. curvisetus could grow normally in the range of 10 ℃ -30 ℃, while K. mikimotoionly grew well between 15 ℃ -25 ℃. Both μmax, and Bf reached the peak values at 20℃ for C. curvisetus and at 25℃ for K. mikimotoi, respectively. These results indicated that compared to C. curvisetus, K. rnikimotoi had a relatively narrow range of suitable temperature and a high optimum temperature （Topt）. Throughout the incubation time, NRA of the two species changed similarly under different temperaaxres. NRA raised slowly at the first 3 -5 days, and then dropped rapidly. The maximum NRA values （NRAmax） usually occurred at the early exponential growth phase, prior to appearing time of μmax and Bf. The relations of μmax, NRAmax and Bf with temperature followed the Shelford tolerance law. All above results suggested that temperature could affect the nitrate assimilation ability of microalgae, and subsequently affect the growth of algae, μmax and the NRAmax per unit volume of the C. curvisetus were higher than those of K. rnikimotoi under the same environmental conditions, indicating that C. curvisetus might have a better ability of absorbing and utilizing nitrate for self-growth than K. mikimotoi.