南溪河大型底栖无脊椎动物群落结构及其季节变化

2020年8月和11月对云南南溪河水系进行了两次大型底栖无脊椎动物调查，共采样到9000余头标本，鉴定出208个物种，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，软体动物次之。水生昆虫中蜉蝣目、双翅目、毛翅目和蜻蜓目为优势类群。南溪河大型底栖无脊椎动物整体生物多样性较高，表现为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、个体数量和密度均显著低于枯水期，但丰水期的生物量显著高于枯水期。优势物种为四节蜉科一种（Baetidae sp.1）、纹石蛾属一种（Hydropsyche sp.1）、蚋科一种（Simuliidae sp.1）、亚非蜉属一种Afromurus sp. 、扁蜉属Heptagenia sp.1，其中前四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1000-1500m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。

Community Structure and Seasonal Variation of Benthic Macroinvertebrates in Nanxi River

Benthic macroinvertebrates were surveyed in Nanxi River, Yunnan Province in August and November 2020. A total of more than 9000 specimens were collected and 208 species, belongs to 4 phyla, 7 classes and 73 families were recorded. The dominated group of benthic macroinvertebrates was aquatic insects, followed by mollusks. Among the aquatic insects, ephemeroptera, diptera, trichoptera and odonata were the dominant aquatic insect groups. The biodiversity of benthic macroinvertebrates in Nanxi River was relatively high, which indicated by the higher biodiversity indexes in most sampling sites. The species composition and individuals of benthic macroinvertebrates were dominated by aquatic insects both in high and low water periods. The species, individuals and density of benthic macroinvertebrates were significantly lower in high water period than in low water period, but the biomass was just the opposite. The dominant species were Baetidae sp.1, Hydropsyche sp.1, Simuliidae sp.1, Afromurus sp.1, Heptagenia sp.1 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 the elevation, substrate and disturbance intensity, the highest diversity occurred at the elevation of 1000-1500m. The species number and density of benthic macroinvertebrates were significantly degraded by the silty sediment and severe disturbance.