长江口九段沙附近水域浮游动物生态特征

Ecological characteristics of zooplankton near the Jiuduansha waters of the Yangtze River estuary

根据1998-2000年长江口九段沙附近水域(30°～32 °N,121°27′～122°30′E)丰水期枯水期6个航次的海洋调查资料,对长江口水域浅水Ⅲ型(网目孔径0.077 mm)和浅水Ⅰ型(网目孔径0.505mm)浮游动物生态特征的变动趋势进行了研究.结果表明:丰水期盐度与浮游动物总丰度有很显著的线性关系,总丰度随着盐度的增加而增加;枯水期盐度与总丰度的关系不明显.同一季节温度与总丰度之间的关系不明显,但从总丰度的季节变化可见,不同水温环境下总丰度的差异依然明显.各年多样性指数(H′)值均小于2;丰水期和枯水期大型浮游动物H′值无论涨潮还是落潮均要大于小型浮游动物.本调查水域浮游动物种类组成简单,种间分布不均匀,优势种突出,主要由淡水生态类型、河口半咸水生态类型、沿岸生态类型和外海生态类型的种类组成.

Ecological characteristics of zooplankton near the Jiuduansha Waters of the Yangtze River estuary were investigated with the data obtained in six cruises from 1998 to 2000. Samplings from Ⅰ net （mesh 0.505mm） and Ⅲ net （mesh 0.077mm） were conducted in drought stage （December） and flood stage （August） separately. It was found that the total abundance of zooplankton was linearly correlated with the salinity in flood stage, showing an increasing total abundance with the increasing of salinity. However, the same correlation was not found in drought stage. In one season, the total abundance was not significantly correlated with temperature （R is 0. 087 for flood stage and 0. 107 for drought stage）, although it varied with the temperature, showing clear seasonal changes. The diversity index was consistently below 2 over years. In both flood stage and drought stage, in spite of flood tide or ebb tide, the sampling with big net always showed a higher diversity index than the sampling with small net. This indicated low zooplankton species diversity, uneven distribution among different species and superiority of the dominant species. According to their ecological characteristics, the zooplankton near the Jiuduansha Waters can be categorized into 4 kinds of ecological groups： fresh water group, estuary brackish-water group, coastal group and oceanic group.