三峡水库澎溪河库湾枝角类的种类组成与时空分布

Species Composition and Spatial-temporal Variation of Cladocerans in Pengxi River Bay of Three Gorges Reservoir

为了解澎溪河枝角类的种类组成、时空分布特点以及三峡水库蓄水对库湾回水末端区域枝角类的影响,为防治三峡水库富营养化和水华发生提供基础资料,于2013年3月(春季)、6月(夏季)、9月(秋季)、12月(冬季)对澎溪河库湾6个断面(河口、双江、黄石、高阳、养鹿和渠口)的枝角类进行了调查。结果显示,4次采样共采集到枝角类7属、7种,透明溞(Daphnia hyalina)、简弧象鼻溞(Bosmina coregoni)、短尾秀体溞(Diaphanosoma brachyurum)为全年优势种,优势度值分别为0.330、0.128、0.034;受上游2个断面(养鹿和渠口)3月份枝角类的影响,澎溪河库湾春、夏、秋、冬枝角类密度(65.9、17.4、4.0、0.6个/L)呈递减趋势,生物量(20.6436、0.6772、0.1072、0.1469 mg/L)基本呈递减趋势;从下游至上游,澎溪河库湾河口、双江、黄石、高阳、养鹿、渠口采样断面枝角类密度(0.5、1.4、11.4、18.8、50.3、49.6个/L)和生物量(0.0348、0.0528、0.6230、1.1538、15.1529、15.3450 mg/L)呈递增趋势。

Pengxi River （also called Xiaojiang River） is located in the middle section of Three Gorges Reservoir and a typical tributary of Three Gorges Reservoir.The water level in Three Gorges Reservoir ranges from 145 m to 175 m and the backwater of Pengxi River extends from 26 km at low water to 72 km at high water.Regardless of water level, the backwater effect causes problems.Slower flow and lower diffusion extend the residence time of pol-lutants and significantly impact the aquatic environment.Cladocera are primary consumers in the plankton food chain and play a key role in nutrient cycling and energy flow throughout the ecosystem.This study characterized the spatial-temporal distribution of cladocerans in the backwater section of Pengxi River and provides insight on the role of Cladocera in the backwater ecosystem created by impoundment of Three Gorges Reservoir.Results provide data to support efforts to control eutrophication and algal blooms in the Three Gorges Reservoir system.A seasonal inves-tigation of cladocerans was accomplished by sampling at 6 stations （ moving upstream from Three Gorges Reservoir：Hekou-HK, Shuangjiang-SJ, Huangshi-HS, Gaoyang-GY, Yanglu-YL, Qukou-QK） in Pengxi River Bay during March, June, September and December of 2013.In qualitative samples, species were identified by microscopic ex-amination.In quantitative samples, cladocerans were counted under a microscope, body length recorded and sam-ple biomass （ mg/L） determined.A total of seven species of Cladocera, belonging to seven genera, were observed in Pengxi River Bay and the dominant species were Daphnia hyalina, Bosmina coregoni and Diaphanosoma brachyurum, with dominance values, respectively, of 0.330, 0.128 and 0.034.From spring to winter, decreases were observed in the density （65.9, 17.4, 4.0, 0.6 ind/L） and biomass （20.6436, 0.6772, 0.1072, 0.1469 mg/L） of cladocerans, mainly affected by the density and biomass in two upstream sections （ YL and QK） in March.Moving in order from the estuary mouth to the beginning of the backwater, the average densities of Clado-cera at the six sampling stations were, respectively, 0.5, 1.4, 11.4, 18.8, 50.3 and 49.6 ind/L, and the corre-sponding average biomasses were 0.0348, 0.0528, 0.6230, 1.1538, 15.1529 and 15.3450 mg/L.Cladoceran populations decreased in the Pengxi River impoundment from upstream to downstream and the decrease was dramat-ic after the two upstream stations.In conclusion, the cladoceran community in Pengxi River Bay affects the struc-ture of the aquatic ecosystem by filter-feeding on phytoplankton.How much Cladocera contributes to the control of algal blooms in Pengxi River Bay is still uncertain, but it warrants continuing investigation.