海洋赤潮藻球形棕囊藻在氮磷富营养下的细胞增殖

利用常见海洋赤潮微藻球形棕囊藻(Phaeocystis globosa)为试验研究材料,以舵海洋微藻营养液为对照(1P1N:磷质量浓度为5×10-3g·L-1.氮质量浓度为75×10-3g·L-1),设置3组富磷和富氮营养处理(3P1N:磷质量浓度为15×10-3 g·L-1,氮质量浓度为75×10-3 g·L-1;1P3N:磷质量浓度为5××10-3 g·L-1,氮质量浓度为225×10-3 g·L-1;3P3N:磷质量浓度为15××10-3 g·L-1,氮质量浓度为225×10-3 g·L-1),利用细胞记数和叶绿素荧光测定等方法研究了藻细胞在不同富磷和富氮条件的增殖情况.结果显示,不同浓度磷和氮营养下的藻体荧光值变化在试验周期内均呈现"S"型曲线,表明藻细胞的生长经历缓慢期,快速期和平缓期3个阶段;同时,不同的富磷和富氮营养条件对球形棕囊藻的叶绿素荧光值有一定的影响,其中在对照1P1N下的藻体荧光值最低,在试验结束时(第10天)只有850 μg·L-1,而在3P1N,1P3N和3P3N条件下的藻体荧光值均达到900 μg·L-1以上,显著高于1P1N下的藻体荧光值,表明富磷和富氮营养可以促进藻细胞的生长增殖,但在试验设置的不同富磷和富氮营养下的藻体荧光值之间没有显著的差异.就不同磷和氮营养条件下的藻最大比生长速率而言,3P3N和3P1N条件下的最大,均达到0.77 d-1,明显高于1P1N和1P3N条件下的藻最大比生长速率(分别只有0.70 d-1和0.69 d-1).此外,试验结束时细胞密度的变化趋势与藻体荧光值相似,富磷和富氮营养条件下的细胞密度显著高于1P1N下的细胞密度,而富磷和富氮营养条件下的细胞密度间也不存在显著的差异.研究结果揭示,水体中的高磷和高氮营养浓度是导致藻细胞大量快速增殖的一个主要因素,而利用叶绿素荧光来测定藻细胞增殖是一种快速、简便,灵敏和可靠的方法,可在今后赤潮监测过程中多加利用,以能及时、准确地预测预报赤潮爆发.从而减少其对环境和经济的影响.

Cell proliferation of Phaeocysis globasa, a red tide causative marine microalga in various phosphorus(P)-and nitrogen(N)-replete conditions

Phaeocystis globosa, a prevalent bloom-forming microalgal species was grown in various phosphorus(P)-replete and ni-trogen(N)-replete conditions, IPIN(f/2 medium): P=5×10-3 g·L-1, N=75×10-3 g·L-1; 3P1N: P=15×10-3 g·L-1, N=75×10-3 g·L-1; 1P3N:P=-5×10-3 g·L-1, N=225×10-3 g·L-1 and 3P3N: P=15×10-3 g·L-1, N=225×10-3 g·L-1, and its cell growth was measured by using chloro-phyll fluorescence determination and cell-counting methods. The results showed that growth curves of Phaeocystis globosa exposed each nutrient conditions exhibited as "S-shaped" curves through out the experiment, indicating the microalgal cells experienced three growth stages, namely slow-growth stage, fast-grow stage and stationary-growth stage. Chlorophyll fluorescence was affected obvi-ously by the P and/or N concentrations. Significantly higher chlorophyll fluorescence was observed in the 3P1N, 1P3N and 3P3N (above 900 μg·L-1) as compared with than that in 1P1N(only 850 μg·L-1), but there were no significant differences in the chlorophyll fluorescence among 3P1N, 1P3N and 3P3N conditions. Besides, remarkably higher specific growth rate was found in 3P3N and 3PIN conditions(both above 0.77 d-1) than IPIN and 1P3N conditions(only 0.70 d-1 and 0.69 d-1 respectively). Finally, changes in the cell density of Phaeocystis globosa exposed to different phosphorus-replete and nitrogen-replete conditions in the termination of experiment were consistent with the changes in chlorophyll fluorescence, with the relatively higher cell density in 3P1N, 1P3N and 3P3N conditions than 1P1N. Our results demonstrate that high concentration of P or/and N in the water is a major factor responsible for the fast growth of microalgal cells, and that measuring the chlorophyll fluorescence in microalgal cells is a quick, simple, sensi-tive and reliable method, hence it should be utilized in the predicting and managing red tides.