Decadal restructuring of driving forces for macroinvertebrate communities in China's Greater Bay Area.

As a vital ecological buffer zone and biodiversity hotspot, the structure and composition of macroinvertebrate communities in estuarine wetlands are undergoing continuous changes due to threats from human disturbances. However, understanding of their temporal dynamics and the driving mechanisms of environmental spatial factors remains limited. In this study, we conducted field sampling in 2013 and 2023 across four representative river sections within the Greater Bay Area (GBA). This study employed diversity indices, zero-model community assembly, and variance partitioning analysis (VPA) to elucidate ecological processes within estuarine macroinvertebrate communities. It further utilized machine learning methods eXtreme Gradient Boosting (XGBoost) to quantify the relative contributions of environmental and spatial factors to community variation. Results indicated that macroinvertebrates in 2013 were dominated by pollution-tolerant annelids, while by 2023, community structure gradually shifted toward a dominance of mollusks and crustaceans. At the Greater Bay Area scale, macroinvertebrate community assembly in 2013 and 2023 was primarily driven by stochastic processes. Additionally, the factors driving β-diversity transitioned from a focus on richness-driven dissimilarity to one of species replacement and community convergence. An analysis of the results from the Shapley additive explanations (SHAP) method indicated that in 2013, broad-scale spatial factors (MEM1, MEM2, MEM4, and MEM7) exhibited the greatest explanatory power. On the other hand, large scale geographical factor (MEM10) and sensitive water quality indicators carbon-to-nitrogen ratio (C/N), conductivity (EC), total dissolved solids (TDS) and ammonia nitrogen (NH3-N) exhibited the strongest explanatory power in 2023. To sum up, our findings provide crucial insights into how the effectiveness of habitat restoration measures can be enhanced through improved environmental conditions and spatial heterogeneity, the importance of multi-stressor exposures and stress responses of macroinvertebrates, and the mechanistic basis for wetland restoration and conservation strategies in GBA.