Spatial-Temporal Pattern and Stability Analysis of Zooplankton Community Structure in the Lower Yellow River, China

In March (spring), June (summer), October (autumn) and December (winter) 2022, zooplankton had been quantitatively investigated in the lower reaches of the Yellow River in China. A total of 29 sampling points which were separated by about 20 km were set up in the survey reach. The purpose of this study is to investigate the seasonal dynamic changes and spatial distribution characteristics of zooplankton community in the Yellow River with high sediment content. The main results are as follows: A total of 119 species of zooplankton were found during the survey, including 70 species of Rotifers, 29 species of Cladocerans and 20 species of Copepods. Because the temperate continental monsoon climate had four distinct seasons, the zooplankton community in the Yellow River showed typical seasonal dynamic changes. There were significant differences in the richness of zooplankton and dominant species in four seasons (P<0.05). There were 15 coexisting species in four seasons, among which Brachionus calyciflorus was the dominant species. The density and biomass of zooplankton were significantly higher in spring and summer than in autumn and winter (P<0.05). The results of multidimensional non-metric ranking (NMDS) based on zooplankton abundance showed four distinct communities, which were spring community, summer community, autumn community and winter community. Affected by human activities (water and sediment regulation, urban sewage input) and natural factors (river and lake water input, estuarine tides), the zooplankton community presented a typical spatial heterogeneity. The density and biomass of zooplankton were significantly lower in estuarine reach than in other reaches. The spatial heterogeneity of zooplankton communities in spring, summer and autumn was significantly different (P<0.05). However, only the estuarine reach had a special zooplankton community in winter. Monte Carlo test results showed that pH, water temperature, electrical conductivity, dissolved oxygen, total nitrogen and total phosphorus were the main water environmental factors affecting the community structure of zooplankton (P<0.05). The reaches of the Yellow River affected by human disturbances have lower zooplankton community stability. Overall, the standing stock of zooplankton was very low (less than 15 ind./L) but the species richness was higher (119 species) in the river with high sediment content, fast flow and oligotrophic levels.