Spatio-temporal patterns of zooplankton community in the Yellow River estuary: Effects of seasonal variability and water-sediment regulation

Zooplankton community is ecological important because of its high sensitivity to environmental changes especially in estuarine areas. The Yellow River estuary (YRE) in China is the fifth biggest estuary in the world with significant seasonal characteristics and anthropogenic influence of Water-Sediment Regulation (WSR). This study investigated the spatio-temporal patterns of zooplankton in the YRE to explore the response of zooplankton to seasonal variation and WSR. Results suggested that the temporal patterns of zooplankton were mainly characterized by seasonal shift of dominant species. Hierarchical cluster analysis and non-metric multidimensional scaling determined summer, summer-autumn and winter-spring three zooplankton assemblages. Zooplankton spatial distributions represented seasonal consistency, in which the abundance generally showed a decreasing gradient from the river mouth to sea. WSR caused a high species replacement rate in July-August (80.36%) and a dramatic abundance decline from 4224.60 ind./m3 to 1541.10 ind./m3 with persistency and hysteresis effect. The high zooplankton abundance moved seaward in spatial distribution after WSR. Summer spatial pattern was determined with two and three zooplankton station assemblages, which was more clear after WSR. Redundancy analysis identified SSS, SST and transparency as important factors structuring zooplankton spatio-temporal patterns, in which SSS was the key one. The results provide a necessary reference for understanding the response of zooplankton community in estuarine areas to spontaneous changes and anthropogenic factors, and can help the protection of estuarine ecosystems and the formulation of hydrological regulatory policies.