N、P营养盐对塔玛亚历山大藻（Alexandrium tamarense）生长的影响

Effects of Limitation of Nitrogen and Phosphorus on the Growth of Alexandrium tamarense

摘要:

模拟自然海水营养盐浓度状况，在N、P浓度分别为10-500μg L^-1 N和0．74—74 μg L^-1 P时，研究N、P双因子限制（N、P浓度同时降低，N：P固定为15：1）及单因子限制（保持N或P为最高浓度，只降低一种营养盐浓度）对有毒赤潮藻塔玛亚历山大藻（Alexandrium tamarense）生长的影响。结果表明，塔玛亚历山大藻细胞能较快进入对数牛长期，但N、P双因子限制能明显影响其生长，在N、P浓度分别低于100 μg L^-1 N和15 μg L^-1 P时，细胞密度无明显增长；而N或P分别受限时，生长态势明显优于N、P同时受到限制的试验组，而且N、P单因子中度限制对生长影响较小。结果说明塔玛亚历山大藻对单因子营养元素限制较强的适应能力，可使其在常常出现单营养冈子限制的自然水体中维持一定生长速率和细胞密度，并有助于滤食该藻的贝类体内麻痹性贝类毒素的积累。

Abstract:

In order to evaluate the growth of A lexandrium tamarense, a toxic harmful algal bloom species, under nitrate and phosphate limitation, five test groups of both N and P limitation （N： 500-10 μg L^-1, P：74-1.5 μg L^-1, N：P=15：1） and nine test groups of only N or P limitation （N：500 μg· L^-1, P：74-0.74 μg L^-1 and P：74 μg L^-1, N: 500-5 μg L^-1 ） were set under laboratory conditions. Though cells ofA. tamarense multiplied exponentially just in the second day after inoculation in most test groups, the growth was obviously inhibited when both N and P limited simultaneously, and the cell densities did not show significant increase under N and P concentrations below 100 txg L^-1 N and 15 txg L^-1 P. However, cells grew significantly better in test groups of single nutrient element limitation than those under both N and P depletion. Furthermore, the growth of A. tamarense was affected less by moderate N or P limitation. The results suggested that the high ability of A. tamarense to adapt single nutrient limitation allows this harmful species to maintain constant growth rate and cell density in natural sea water, in which single nutrient limitation usually occurs, and thus helps shellfishes, feeding on A. tamarense, to accumulate paralytic shellfish poisoning （PSP）.