大亚湾海域浮游动物种类组成和优势种的季节变化

为全面掌握南海北部大亚湾海域浮游动物的群落特征。利用2007—2008年在大亚湾开展的4个航次124个站次的海洋生物调查数据和历史资料,通过数据统计分析,对浮游动物种类组成和优势种进行研究,结果表明:(1)大亚湾浮游动物种类组成的季节变化明显、种类更替频繁;(2)优势种组成简单,季节变化明显,单一种的优势地位显著。与过去相比,大亚湾海域浮游动物群落的组成基本稳定,但种类和优势种的更替率均呈现逐步增大的趋势,浮游动物优势种组成趋于简单、单一种优势地位明显提高。大亚湾生态环境随季节的变幅增强,群落的稳定性明显下降。海水温度的升高,改变了大亚湾暖水性浮游动物种类的生活周期;而且营养水平的提高也促使赤潮种类夜光虫数量的增加。

Seasonal succession of zooplankton species compositions and dominant species in the Daya Bay, northern South China Sea

The zooplankton species compositions and dominant species in the Daya Bay were studied based on 124 samples collected from seasonal surveys conducted in December 2007 and March, May, and September 2008. A total number of 284 zooplankton species were recorded in the surveys. We found large seasonal changes in zooplankton compositions with an average ratio of 62.3% of species seasonal subrogation. We also found that there were apparent dominant species and the dominant species changed greatly between seasons. Noctiluca miliaris was the first dominant species in winter and spring and Dolioletta gegenbauri and Sagitta enflata dominated in the other two seasons, while the other 13 species were seasonal dominant species only found in a single season. The clear seasonal succession of zooplankton compositions and dominant species was a reflection of the increased amplitude of seasonal variations in environmental conditions in the Daya Bay. Compared with past records, the seasonal subrogation ratio of zooplankton species has been increased, the dominant species changed from Copepoda to Protista, and their dominance became higher. This indicates that the stability of zooplankton community has been reduced. The increased water temperature in the Daya Bay has changed the life cycle of the warm-water zooplanktons. The peak season of zooplankton abundances shifts from August to May or October when water temperature is lower, the warm-water zooplankton species occur in all seasons, and the amplitudes of seasonal variations in their abundances have been reduced. Because of the increased nutrient levels in the Daya Bay, the dominance of the red-tide species of Noctiluca miliaris has been greatly increased, especially in winter and spring when the water temperature is lower, and the highest abundances are found in the waters affected warm water discharges from the Daya Bay Nuclear Power Plant.