Disentangling the Drivers of Fish Community Variation in a Highly Urbanized Estuary Based on Hierarchical Modeling of Species Communities ( HMSC )

ABSTRACT

Biodiversity conservation and management in highly urbanized estuaries have garnered widespread global attention. However, the environmental response mechanisms of fish communities in these estuaries remain poorly understood, hindering their ecological health and sustainable development. Here, we utilized Hierarchical Modeling of Species Communities (HMSC), a burgeoning and powerful framework, jointly investigating how the species occurrences, species traits, and spatiotemporal structure of fish communities respond to environmental variables in the Pearl River Estuary (PRE). It exhibited seasonal variation in species composition, taxonomic diversity, functional diversity, and functional‐space occupancy of fish communities, and several CWM traits showed directional seasonal shifts. Furthermore, the HMSC framework showed that environmental filtering was the primary driver of the spatiotemporal dynamics in fish community. Salinity, pH, and phosphate were identified as key environmental drivers of species distributions and trait‐mediated responses. Functional traits showed contrasting responses along the phosphate gradient, whereas habitat‐level residual species associations revealed distinct positive and negative co‐occurrence patterns that reflect shared environmental filtering rather than stochastic assembly. The study elucidates the environmental response mechanisms of fish community dynamics by integrating taxonomic and functional diversity perspectives, offering new insights into the assembly of estuarine fish communities.