三峡工程三期蓄水初期长江口水域春季浮游动物群落特征及其与环境的关系

三峡工程于2010年10月26日达到三期正常蓄水位,为了研究三期蓄水后初期长江口的生态环境特征,于2011年4月对长江口水域24个站位进行了浮游动物的采集,分析了其种类、丰度、优势种及其与环境的关系.结果表明,调查海域共发现浮游动物97种(含20种浮游幼体),其中,桡足类33种,水母类13种,介形类5种,毛颚类5种,还有一些其它浮游种类.夜光虫和中华哲水蚤是该水域的绝对优势种.根据各站位浮游动物种类组成及其丰度,采用聚类分析法将该水域的浮游动物分为4组群落区域:外海高盐区、冲淡水和外海水混合区、长江口南支附近、长江口北支附近.物种丰度和多样性在空间分布上呈相反的趋势,在长江冲淡水和外海水的混合水域丰度最高,多样性指数最低.物种与环境的CCA(典范对应分析)显示,影响长江口春季浮游动物群落结构的主要环境因子为盐度、营养盐和水温.

Spring character of zooplankton community and its relation to environmental factors in Yangtze estuary right after the third-stage impoundment of Three Gorges Reservoir

The third-stage impoundment of the Three Gorges Reservoir was reached on October 26, 2010. In order to understand the ecosystem features of the Yangtze estuary soon after the third-stage impoundment, zooplankton samples were collected in 24 sites of Yangtze estuary in April, 2011. The character of zooplankton community such as dominant species, abundance and diversity were analyzed. Meanwhile, the relation between species composition and environmental factors was investigated. The results showed that a total of 97 species (including 20 pelagis larvae) were identified in the water, including 33 kinds of copepods, 13 kinds of jellyfish, 5 kinds of Ostracods, 5 kinds of Chaetognatha, and some other species. The Noctiluca and Calanus sinicus were the predominant species. According to zooplankton composition and abundance, the sample sites in Yangtze estuary could be classified into four groups: high salt area off the coast, mixed zone of freshwater and salt water, the area near the south branch of the Yangtze estuary, the area near the north branch of the Yangtze estuary. The species abundance showed opposite trend to the diversity with respect to their spatial distribution. The abundance was the highest in the mixed zone, but the diversity was the lowest in this area. The first two axes of canonical correspondence analysis (CCA) collectively explained 68.4% of the species-environment variation. The main environmental factors affecting community character of zooplankton in Yangtze estuary were salinity, nutrients and water temperature.