Abstract: Zhangjiang Estuary is a typical mangrove-estuary complex ecosystem along the coast of southeast China. The macrozoobenthic community plays a significant role in maintaining material circulation and energy flow. In August 2021 and January 2022, we conducted quantitative sampling of macrobenthos and environmental factor determination at six stations in the subtidal zone of Zhangjiang Estuary. Combined with functional trait analysis and Canonical Correspondence Analysis (CCA), we explored the spatiotemporal variations and driving mechanisms of the functional structure of macrozoobenthic community. A total of 37 macrozoobenthic species were collected, including 18 polychaete species, 13 crustacean species, and 2 gastropod species. There were pronounced seasonal and spatial variations in the macrozoobenthic communities. The functional diversity indices (FRic and FEve) of macrozoobenthic community in winter were higher than those in summer. Functional diversity indices of macrozoobenthic community increased from the upper estuary to the offshore area. Mantel test and CCA analysis indicated that salinity and nutrients were the key environmental factors affecting the spatiotemporal variation of community functional structure, with the summer community being primarily influenced by nutrients and the winter community being driven by salinity and pH. Environmental factors and anthropogenic activities (e.g., nuclear power plant construction) synergistically drive functional trait divergence by altering sediment properties and water nutrient structure. In conclusion, environmental factors and human activities jointly drive the changes in macrozoobenthic community in the subtidal zone of the Zhangjiang Estuary. We recommended that nutrient input control be prioritized and that functional diversity indices should be incorporated into the conservation and restoration of mangrove-estuary ecosystems, which would favor the assessment of ecosystem health and recovery potential.

Key words: macrozoobenthos, functional diversity, environmental factor, mangrove, Zhangjiang Estuary