长江中下游湖群大型底栖动物群落结构及影响因素

长江中下游地区是我国淡水湖泊分布最为密集的区域,其中面积大于10 km²的湖泊总面积占相同级别中国淡水湖泊总面积的51.3%。目前对本地区湖泊大型底栖动物研究主要是关于单个湖泊或几个湖泊之间的比较,将区域内湖泊作为一个整体来分析的研究较少。为揭示现阶段长江中下游浅水湖泊底栖动物群落现状及其主要影响因素,于2008年和2009年夏季对本地区5个湖群69个湖泊大型底栖动物和水化学进行了调查,并分析区域过程和局域环境条件在决定该地区底栖群落结构中的相对重要性。结果表明水体矿化度、电导率及氮磷指标在不同湖群间具有显著差异,而高锰酸盐指数、叶绿素a及营养状态指数无显著差异。密度方面,以寡毛类和摇蚊幼虫为优势类群的湖泊共46个,占总数量的66.7%,以螺类为优势类群之一的湖泊16个,占总数量的23.2%;生物量方面,以螺类为优势的湖泊数量最多(33个),占总数量的46.4%,但以寡毛类和摇蚊幼虫占优势的湖泊亦有27个,占总数量的39.1%,双壳类仅在9个湖泊占据优势。典范对应分析结果表明该地区底栖动物群落结构是局域环境条件和区域过程共同作用的结果,两类因子共解释了33.9%的底栖动物群落变异,其中局域环境因子占被解释量的48.1%,空间变量占35.4%。空间变量较高的解释量表明对整个长江中下游地区湖泊而言,区域过程对底栖动物的分布也起着非常重要的作用。

Structure of macrozoobenthos in lakes along the Yangtze River and relationships with environmental characteristics

In the middle and lower reaches of the Yangtze River, there are 108 freshwater lakes with surface area larger than 10 km², accounting for 51.3% of the total freshwater lake area in China. However, few studies of macrozoobenthos were conducted at the regional scale, contrasting with many studies focused on individual or several lakes. To elucidate macrozoobenthic community structure and their relationships with spatial and environmental factors in shallow lakes along the Yangtze River, physicochemical parameters and macrozoobenthos were measured in 69 lakes of this region during summer in 2008 and 2009.We also evaluated the relative influences of local environmental conditions versus regional processes on macrozoobenthic community structure. The results showed that total dissolved solids (TDS), conductivity, nitrogen and phosphorus differed significantly among the five lake districts, but not for chemical oxygen demand (COD_Mn), chlorophyll a and Trophic State Index (TSI) index. In terms of density, 46 lakes (66.7% of the total 69 lakes) were dominated by Oligochaeta and Chironomidae, and Gastropoda was one of the dominant taxa in 16 lakes. With respect to biomass, 27 lakes were also dominated by Oligochaeta and Chironomidae, and 33 and 9 lakes were dominated by Gastropod and Bivlavia due to their relatively large body size, respectively. Canonical correspondence analyses (CCA) showed that macrozoobenthic community structure reflected the influence of local conditions (TSI, Macrophytes, Chl a, TDS) as well as regional processes. Only 33.9% of variation in a density matrix was explained by local environmental conditions and regional processes. Of the total explained variation, 48.1% and 35.4% were purely related to local environmental parameters and spatial variables, respectively. The high proportion of variation related to spatial variables indicated the importance of regional processes on spatial patterns of macrozoobenthic assemblages in this region.