Zooplankton community structure and influencing factors in Weihe River mainstem and its tributaries from the northern foot of Qinling Mountains

Abstract

浮游动物作为食物链中重要的初级消费者，其群落结构特征是水生态系统健康评价的重要指标之一. 本研究于2017年秋季和2018年春季对渭河干流及秦岭北麓五条典型支流开展了系统的水环境及浮游动物群落调查. 结果表明，渭河干流营养盐浓度整体高于秦岭北麓支流，干流浊度远高于支流. 两次调查共鉴定出浮游动物种类数136种(原生动物65种，轮虫44种，枝角类15种，桡足类12种)，其中2017年秋季渭河干流浮游动物种类数、密度和生物量分别为14种、9.02 ind./L和0.0051 mg/L，秦岭北麓支流为37种、42.78 ind./L和0.0229 mg/L；2018年春季渭河干流浮游动物种类数、密度和生物量分别为52种、292.89 ind./L和0.1734 mg/L，秦岭北麓支流为68种、70.15 ind./L和0.0508 mg/L. 秋季渭河干流下游浮游动物种类数、密度和生物量最低，而春季随上、中、下游三者均依次增大；秋季秦岭支流中罗敷河浮游动物密度和生物量最高，而春季灞河最高. 春、秋两季干支流间浮游动物优势种差异较小，但秋季优势种种类数少于春季. 秋季渭河干流中游Shannon-Wiener指数、物种丰富度指数和物种均匀度指数最高，而春季下游最高；秋季秦岭北麓支流石堤河3个指数均最高，而春季灞河Shannon-Wiener指数和物种均匀度指数最高，石堤河物种丰富度指数最高. 典范对应分析表明渭河干流与秦岭北麓支流浮游动物群落结构主导因素均存在季节差异. 本研究揭示了渭河干流与秦岭北麓典型支流的浮游动物群落特征及其影响因素，可为渭河流域环境监测和生态保护提供数据支撑.;Zooplankton is an important primary consumer in the food chain, and its community structure is one of the important indicators for the health evaluation of aquatic ecosystems. A systematic survey of water environment and zooplankton was carried out in the Weihe River mainstem and its five tributaries from the northern Qinling Mountains during autumn 2017 and spring 2018. The nutrient concentrations of the Weihe River mainstem were higher than those of the five tributaries, while turbidity of the mainstem was 10-100 times higher than those of the tributaries. A total of 136 species of zooplankton (65 species of protozoa, 44 species of rotifers, 15 species of cladocerans, and 12 species of copepods) were identified in the two surveys. Among them, the number, density and biomass of zooplankton in the mainstem of the Weihe River mainstem in autumn 2017 were 14 species, 9.02 ind./L and 0.0051 mg/L, while tributaries were 37 species, 42.78 ind./L and 0.0229 mg/L, respectively. The number of species, density and biomass of zooplankton in the Weihe River mainstem in spring 2018 were 52 species, 292.89 ind./L and 0.1734 mg/L, while tributaries were 68 species, 70.15 ind./L and 0.0508 mg/L, respectively. In autumn, the number of zooplankton species, density and biomass in the lower reaches of the Weihe River mainstem were the lowest, while those increasing in the rank from upper, middle, to lower reaches of the Weihe River mainstem in spring. The density and biomass of zooplankton in the Luofu River were the highest in autumn, and those in the Bahe River highest in spring. The difference in dominant species of zooplankton between the trunk and tributaries of spring and autumn is relatively small, but the number of dominant species in autumn is less than that in spring. Canonical correspondence analysis revealed seasonal variance in the dominant factors of the zooplankton community structure in the Weihe River mainstem and the five tributaries. This study not only revealed the correlation between zooplankton community structure and environmental factors in the Weihe River mainstem and its five tributaries, but also provided key data for environmental monitoring and ecological protection in the Weihe River Basin.