低温和高温下颗石藻(Pleurochrysis sp.)种群生长特征及生化变化

Population growth characteristics and relevant biochemical changes of coccolithophorid (Pleurochrysis sp.) at low and high temperatures

以浙江省象山港虾塘藻华中分离的一种颗石藻(Pleurochrysis sp.)为对象,对温度差异造成的藻类在种群水平上的增殖特征,以及相应增殖过程中细胞的生化特征变化进行了比较研究,包括:差异温度(低温7℃,高温25℃)下,盐度(5,15,30,45)和光照(低光照<2μE·m-2s-1,高光照100μE·m-2s-1)不同组合条件影响下的种群增殖特征;差异温度下,种群生长过程中的氮、磷消耗特征,细胞Chl-a的变化特征,以及细胞总多糖变化特征比较。结果显示:颗石藻在低温低光照条件下,不同盐度水平中均维持存活,没有种群增殖;低温高光照下,经低温适应期后,种群可以增殖。高温低光照导致各组种群迅速衰退。高温高光照下颗石藻快速增殖。相同光、温条件下,盐度15,30,45的种群增殖趋势相似,盐度5不利于种群增殖。在其它环境因子相同的条件下,温度差异导致颗石藻在种群增殖策略上不同,其间相应的生化特征也存在差异:低温中,颗石藻耐受适应期长,种群生长率低下,期间的氮、磷消耗率低,细胞Chl-a含量降低,细胞总多糖含量高于高温组;低温适应后,颗石藻种群增殖,且达到稳定的增殖速率,增殖期间大量消耗氮、磷营养盐,细胞Chl-a含量渐增,细胞总多糖含量维持相对稳定。高温中,颗石藻快速增殖,初期生长率高,大量氮、磷营养盐在此期中消耗,细胞Chl-a含量渐增,细胞总多糖含量低于低温组,种群生长后期细胞总多糖出现累积。

Population growth rate, nutrient consumption, and the chlorophyll a and polysaccharide content of the coccolithophore Pleurochrysis sp. -isolated from a bloom in a shrimp pond near Xiangshan Bay China-were studied as a function of temperature, irradiance, and salinity. The environmental parameters include two temperatures （ low, 7℃;high, 25℃）, two irradiance levels （low, 〈2 μE·m^-2s^-1;high, 100μE·m^-2s^-1）, and four salinities （5, 15, 30, 45）.At low temperature-low irradiance, Pleurochrysis sp. survived but did not grow, and at high temperature-low irradiance the cells died. However, Pleurochrysis sp. grew well under high irradiance at both high and low temperatures. Growth curves show that Pleurochrysis sp. has different growth patterns at high and low temperature. At low temperature, the cells experience a lag phase of very slow growth, low nitrogen and phosphorus consumption, and a decrease in Chl-a content, followed by a rapid grow phase with a large consumption of nitrogen and phosphorus, a gradual increase of Chl-a, a higher polysaccharide content than that at high temperature, but no further polysaccharide accumulation. At high temperature, Pleurochrysis sp. grows very fast from the outset with rapid consumption of nitrogen and phosphorus, a slight increase in Chl-a content. Polysaccharides accumulate later during the subsequent stationary growth phase. Pleurochrysis sp. growth pattern was similar in 45, 30, and 15, except at 5.