无定河流域浮游动物群落结构特征及水质生物评价

为探究无定河流域浮游动物群落结构特征及其水质状况,于2021年春秋季对无定河干流、6条支流及3个淤地坝水体展开生态调查。共鉴定出浮游动物125种,其中原生动物40种、轮虫54种、枝角类15种、桡足类16种,秋季物种数(103种)高于春季(76种),均以小型浮游动物为主。浮游动物优势种共31种,以臂尾轮虫和龟甲轮虫等富营养型水体指示生物居多,春季优势种优势度整体高于秋季。春季浮游动物平均密度(360.9个/L)和平均生物量(0.600 mg/L)均高于秋季(83.6个/L、0.298 mg/L),且春秋季淤地坝水体中浮游动物平均密度和生物量均高于河流。非度量多维尺度分析也表明:河流与淤地坝2种水体中的浮游动物群落分布存在差异,采用冗余分析进一步探明,主要差异为河流和淤地坝2种水体中影响浮游动物群落分布的环境因子不同,其中化学指标(溶解氧、盐度、亚硝氮、硝态氮、溶解磷、叶绿素a)和物理指标(水深、透明度、浊度)分别是影响河流和淤地坝水体中浮游动物群落结构的主要环境因子。水质生物评价结果显示,春秋季水质均为无定河干流最优,支流次之,淤地坝水质最差,且干流中下游水质优于上游。

Characteristics of Zooplankton Community Structure and Bioassessment of Water Quality in the Wuding River Basin

In order to explore the characteristics of zooplankton community structure and water quality in the Wuding River Basin, an ecological survey was carried out on the mainstream,6 tributaries and 3 check dams of the Wuding River in the spring and autumn of 2021. A total of 125 species of zooplankton were identified,including 40 species of protozoa,54 species of rotifers,15 species of cladocerans and 16 species of copepods. The number of species in autumn (103 species) was higher than that in spring (76 species), all of which were dominated by small zooplankton. There were 31 dominant species of zooplankton,most of which were eutrophic water body indicator organisms such as Brachiocephalus rotifers and KeratelIa rotifers. Meanwhile,the dominance of dominant species in spring was generally higher than that in autumn. The average density (360. 9 ind./L) and average biomass (0. 600 mg/L) of zooplankton in spring were higher than those in autumn (83. 6 ind./L,0. 298 mg/L), and the average density and biomass of zooplankton in check dam water body were higher than those in the rivers in two seasons. Non-metric multidimensional scaling analysis also showed that there were differences in the distribution of zooplankton communities in the two water bodies of rivers and check dams. Redundancy analysis was used to further prove that the main difference was the different environmental factors affecting the distribution of zooplankton communities in the two water bodies of river and check dam. Among them,chemical indicators (dissolved oxygen,salinity,nitrous nitrogen,nitrate nitrogen,dissolved phosphorus,and Chlorophyll a) and physical indicators (water depth,transparency,and turbidity) were the main environmental factors of zooplankton community distribution in river and check dam water bodies,respectively. The results of biological evaluation of water quality showed that the water quality of the mainstream of the Wuding River was the best in both seasons,followed by the tributaries,and the water body of the check dam was the worst,and the water quality of the middle and lower reaches of the mainstream was better than that of the upper reaches.