Copepods are key secondary producers in marine food webs, but studies that focus on individual species often miss the functional roles that shape community responses to environmental change. The Yangtze River Estuary is a highly dynamic system with strong salinity gradients, heavy nutrient loading, and distinct seasonality, creating heterogeneous habitats that support copepod assemblages with diverse ecological strategies. A trait-based functional group perspective is therefore needed to better capture the link between community structure and estuarine processes.
     In this study, copepods are classified by body size (small, medium, large) and feeding strategy (feeding-current, cruise, and ambush feeders), yielding nine functional groups. Long-term survey data from the estuary are paired with concurrent hydrological observations, including temperature, salinity, dissolved oxygen, and nutrients, through a spatiotemporally constrained interpolation procedure. Ensemble modeling using the Biomod2 platform integrates multiple algorithms—such as Random Forest, GAM, and GBM—to relate continuous abundance to environmental drivers and to account for nonlinear, interactive effects.
     This study reveals distinct spatiotemporal patterns and multi-year trends of copepod functional groups across the Yangtze River Estuary. Temperature, salinity, and nutrient availability emerge as primary drivers, with their modes of action differing among functional groups. Systematic comparison of multiple algorithms yields optimized models for copepod abundance and a robust framework for projecting future distributional shifts. By characterizing communities through functional groups rather than taxonomic entities, the approach captures mechanistic linkages between community dynamics and ecological processes, providing new insights into zooplankton ecology in this highly dynamic estuarine system.

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