长江口潮下带春季大型底栖动物的群落结构

2005年4月对长江口全区域潮下带共10个采样站位的大型底栖动物进行了调查。调查采获大型底栖动物38种,分属5个生态类型,种类数较少,河口外缘站位种类数多于口内站位。各站位大型底栖动物的平均丰度为32.9个/m2、平均生物量为5.035g/m2(湿重);与20世纪七八十年代相比,平均生物量显著降低;口外缘站位的总丰度和总生物量均高于口内站位。环境因子相关分析表明,盐度是决定长江口大型底栖动物种类分布最重要的环境因子。群落聚类、标序分析显示,春季长江口潮下带大型底栖动物群落结构空间分异明显,完全符合目前长江口支、港、槽“三级分汊”的空间格局。其中,北支的大型底栖动物以混合高盐水种类为主,而南支则以淡水和半咸水种类为主。南支的南北槽分界处内外站位的群落差异也由盐度决定,因为靠近口内的群落均受长江冲淡水影响较大;而口外站位群落则受咸淡水影响。南支的南北港分界点内外的群落差异则主要受长江来水的影响,原因在于处在港分界点以内的群落所在区域,直接受长江来水的冲刷,底质环境极不稳定;而港、槽分界点之间的群落所在区域由于河口上段的诸多明暗沙体的阻挡,水势较为稳定,所以底质环境较稳定,从而使得港、槽分界点之间的群落出现了更多的沙蚕等底质环境类型种类。

Community Structure of Macrobenthic Fauna in Subtidal Areas of the Yangtze River Estuary in Spring

Samples of subtidal macrobenthic fauna were collected and environmental factors were measured in the Yangtze River Estuary in April,2005.The community structure of macrobenthic fauna and its correlation with environmental factors were analyzed.Thirty-eight species were identified,belonging to five ecological assemblages.The total species numbers were low,but were higher in the outer sampling sites of the estuary.The average abundance was 32.9 ind./m2 and the average biomass was 5.035 g/m2(fresh weight)at all sampling stations.Compared with historic data from the 1970s and 1980s,the community structure of macrobenthic fauna has changed obviously and the biomass has decreased rapidly.Total abundance and biomass of the species were obvious higher at the outer sampling sites of the estuary.Salinity was the main factor affecting the distribution of the macrobenthic fauna.The distribution of the macrobenthic fauna communities corresponded to three structural orders of the Yangtze River Estuary.