南溪河大型底栖无脊椎动物群落结构及其季节变化

Community Structure and Seasonal Variation of Benthic Macroinvertebrates in Nanxi River

研究南溪河流域大型底栖动物的群落结构及其季节动态,为该流域生物多样性保护和管理提供科学依据。2020年8月和11月对云南南溪河水系进行了2次大型底栖无脊椎动物调查,共采集到物种个体数9 421个,鉴定出208种(属),隶属4门7纲73科。该区域大型底栖无脊椎动物以水生昆虫为主,共171种,占82.2%;软体动物次之,28种,占13.5%。水生昆虫中蜉蝣目、双翅目、毛翅目和蜻蜓目为优势类群。大多数样点的生物多样性指数值处于较高水平。无论丰水期还是枯水期,大型底栖无脊椎动物在物种组成和个体数量上均以水生昆虫为主,丰水期的物种数、个体数量和密度(125种、4 026个和307个/m^(2))均显著低于枯水期(153种、5 395个和347个/m^(2)),但丰水期的生物量(5.71 g/m^(2))高于枯水期(3.23 g/m^(2))。物种优势度由高到低分别为四节蜉科一种(Baetidae sp.)、纹石蛾属一种(Hydropsyche sp.)、蚋科一种(Simuliidae sp.)、亚非蜉属一种(Afromurus sp.)、扁蜉属一种(Heptagenia sp.),其中前4种在丰水期和枯水期均为优势种。南溪河大型底栖无脊椎动物多样性受到海拔、河道底质和干扰强度的影响,在海拔1 000~1 500 m的地区多样性最高,淤泥质底质和重度干扰使大型底栖无脊椎动物的物种数和密度显著降低。

In this study,we explored the community structure and seasonal dynamics of benthic macroinvertebrates in Nanxi River and analyzed the influence of environmental factors on the community,aiming to provide scientific evidence for the conservation and management of biodiversity in the river basin.The study was based on a survey of benthic macroinvertebrates at 35 sampling sites in Nanxi River,Yunnan Province in August(flood season)and November(dry season)2020,focusing on the species composition,number of individuals and spatial distribution.Environmental factors were investigated synchronously,including elevation,river width,water depth,substrate type and human disturbance.A total of more than 9421 specimens were collected during the investigation,including 208 species that belonged to 73 families,7 classes and 4 phyla.The dominant group of benthic macroinvertebrates was aquatic insects(171 species,82.2%),followed by mollusks(28 species,13.5%).Among the aquatic insects,Ephemeroptera,Diptera,Trichoptera and Odonata were the dominant taxa.The diversity indices of benthic macroinvertebrates at most sampling sites were high,indicating high benthic macroinvertebrate biodiversity in Nanxi River.The species composition and individual numbers of benthic macroinvertebrates were dominated by aquatic insects in both high and low water periods.Species number,number of individuals and benthic macroinvertebrate density were significantly lower in the high water period(125 species,4026 ind,307 ind/m^(2))than in low water period(153 species,5395 ind,347 ind/m^(2)),but biomass in the flood season(5.71 g/m^(2))was significantly higher than in the dry season(3.23 g/m^(2)).The dominant species were Baetidae sp.,Hydropsyche sp.,Simuliidae sp.,Afromurus sp.and Heptagenia sp.,among which the first four species were dominant both in high and low water periods.The diversity of benthic macroinvertebrates in the Nanxi River was affected by elevation,substrate and human disturbance intensity and the highest diversity occurred in the river section in the elevation range of 1000-1500m.The diversity and density of benthic macroinvertebrates were significantly degraded when the substrate was heavily silted and by severe disturbances due to human activities.