山地河流浅滩深潭生境大型底栖动物群落比较研究——以重庆开县东河为例

浅滩和深潭是山地河流中常见的河流生境结构。2011年7月,在重庆开县东河上游双河口-杉木桥河段,选择21个浅滩和深潭,调查大型底栖动物,研究影响不同生境中底栖动物组成、分布和多样性的生态机理。结果表明:调查河段浅滩和深潭中大型底栖动物分别为31种和24种,密度分别为450.62 个/m²和86.24 个/m²,生物量分别为2.88 g/m²和0.55 g/m²。浅滩有指示种11种,即纹石蛾(Hydropsyche sp.)、假蜉(Iron sp.)、假二翅蜉(Pseudocloeon sp.)、舌石蛾(Glossosoma sp.)、高翔蜉(Epeorus sp.1)、背刺蜉(Notacanthurus sp.)、Heterocloeon sp、锯形蜉(Serratella sp.)、朝大蚊(Antocha sp.)、等蜉(Isonychia sp.)、溪颏蜉(Rhithrogena sp.)。深潭指示种仅蜉蝣(Ephemera sp.)和黑大蚊(Hexatoma sp.)两种。刮食者为两类生境的优势功能摄食类群。浅滩中滤食者和刮食者比例显著高于深潭,而收集者和捕食者显著低于深潭。两类生境中大型底栖动物群落结构差异显著。浅滩中大型底栖动物的密度、生物量、丰富度指数、Shannon-Wiener 指数、改进的Shannon-Wiener指数均明显高于深潭。受地貌形态、水力特征和冲淤变化规律影响的生境稳定性和异质性差异是导致大型底栖动物群落差异的主要原因。

Comparison study on macroinvertebrate assemblage of riffles and pools:a case study of Dong River in Kaixian County of Chongqing, China

Riffle and pool, which exhibit very different physical characteristics (such as depth, velocity, substrate), are basic and common habitat units in mountain rivers. The benthic macroinvertebrate is an important connector among the different trophic levels of stream ecosystem and its community could be easily affected by variation of physical characteristics of microhabitat. However, previous researches did not always demonstrate a clear difference of community structure and diversity between riffle and pool macroinvertebrate. Dong River is a typical mountain stream which is located in a karst area of southwestern China, namely Kaixian County of Chongqing. In order to study variations in structure, composition and diversity between riffle and pool macroinvertebrate assemblage, we chose twenty one pairs of riffles and pools to investigate benthic macroinvertebrate species in upstream of Dong River in July 2011. Our results indicated that the difference of water quality was not significant between the two habitats. However, the riffle habitat not only had a wider water surface and faster flow velocity, but also contained bigger substrate than those of the pool habitat. The number of species was thirty one in riffles and twenty four in pools. Density and wet biomass of macroinvertebrate assemblage in riffles were 450.62 ind/m² and 2.88 g/m², respectively, comparing to 86.24 ind/m² and 0.55 g/m² in pools. Mayfly was the group with the highest density, abundance and species richness in both habitats. Virtually all species were more abundant in riffles than those in pools, except chironomids, Ephemera sp and Hexatoma sp which were more abundant in pools. Indicator Species Analysis indicated that a greater number of taxa, including Hydropsyche sp, Iron sp, Pseudocloeon sp, Glossosoma sp, Epeorus sp2, Notacanthurus sp, Heterocloeon sp, Serratella sp, Antocha sp, Isonychia sp and Rhithrogena sp, were restricted to riffles, while only two species, Ephemera sp and Hexatoma sp, were indicator species of pools. Kruskal-Wallis Test indicated that relative abundance of each functional feeding group was significantly different between the two habitats. Scraper was the dominant functional feeding group in both habitats, while shredder had the lowest relative abundance. Relative abundance of functional feeding groups between riffle and pool were significantly different except that of shredder. Riffles exhibited significantly higher percentage of collector-filterer and scraper, while percentage of collector-gatherer and predator in pools were significantly higher than that of riffles. Detrended Correspondence Analysis indicated that the difference of macroinvertebrate community structure was obvious between the two habitats. Density, wet biomass, species richness, Shannon-Wiener index and Improved Shannon-Wiener index of riffles were significantly higher than those of pools, which was similar with former researches conducted in mountain stream with stony substrate. Pool characterized by small and loose substrate is unstable and vulnerable habitat for benthic macroinvertebrate to resist fast flow during the flooding period. However, bigger substrate of riffle as a result of erosion creates a much more diverse and stable for macroinvertebrate to escape predators and disturbance of scouring. Therefore, habitat stability and heterogeneity affected by habitat morphology, hydraulic characteristics and erosion/deposition pattern may be the major explanation.