Variations and drivers of zooplankton community β diversity in the Yangtze River Estuary

To investigate the spatiotemporal patterns of zooplankton community β diversity and reveal the environmental driving mechanisms in the Yangtze River Estuary, we analyzed the structure of the zooplankton community and β diversity and its components based on the survey data of the Yangtze River Estuary and adjacent waters in spring and autumn of 2020-2021. We further explored the effects of environmental factors and spatial distance on the formation of β diversity patterns by using the Mantel test and the generalized dissimilarity model (GDM). A total of 99 zooplankton species were recorded. Among all the species, 40 species were copepods, accounting for 40.4% of the total species, and were the dominant group. The abundance values were higher in spring than in autumn, and the abundance distribution in spring exhibited a trend of higher in nearshore areas and lower in offshore areas, while the abundance distribution in autumn showed significant spatial heterogeneity. Sinocalanus sinensis, Schmackeria poplesia, Tortanus vermiculus, and Sinocalanus dorrii had relatively high occurrence frequencies at all the stations. Turnover components dominated the zooplankton community β diversity in both spring and autumn, indicating that species replacement was the main source of community variations. The mean value of β diversity (0.639 vs 0.519) and the contribution rate of the turnover component (78.1% vs 70.5%) in spring were both higher than those in autumn. The results of Mantel test showed that spatial distance and salinity were the key factors influencing β diversity and its turnover component of zooplankton communities, suggesting that both diffusion limitation and salinity gradient jointly driving the spatial differentiation of the community. The GDM model revealed that the community construction in spring was jointly influenced by environmental selection and diffusion limitation, with salinity, pH, and inorganic nitrogen being the main environmental contributing factors, with contribution rates of 31.7%, 18.4%, and 8.3% respectively. In autumn, environmental selection played a dominant role, with the influence of salinity and active phosphate being relatively higher, with contribution rates of 50.2% and 18.0% respectively.