Response of macrobenthic diversity and functional traits to eutrophication pressures: Insights from three subtropical...

Eutrophication poses a critical threat to estuarine ecosystems globally, yet its effects on macrobenthic taxonomic and functional diversity remain insufficiently understood, particularly in subtropical regions. This study investigates how eutrophication shapes taxonomic and functional diversity of macrobenthic communities in three subtropical estuaries in China: the Pearl River Estuary (PRE), Moyang River Estuary (MRE) and Jianjiang River Estuary (JRE). Based on the Trophic Index (TRIX), PRE, MRE, and JRE exhibit high, medium, and low trophic status, respectively. Significant differences in species composition are observed among the three estuaries and trait composition differs markedly between highly and weakly eutrophic estuaries, indicating that eutrophication is a key driver of macrobenthic community structure. In the highly eutrophic PRE, macrobenthic communities are characterized by first-order opportunistic species, carnivores, epifauna, and exhibited reduced body size, lower richness, abundance, and biomass. In the moderately eutrophic MRE suspension feeders, burrow-dwelling, and tolerant species are dominant. Weakly eutrophic JRE shows the highest richness and abundances, and deposit feeders are dominant. Environmental factors, particularly dissolved inorganic phosphorus and sediment properties strongly influence trait distributions. These findings highlight the value of trait-based approaches in clarifying the complex macrobenthic responses to eutrophication and in supporting assessment and management of subtropical estuarine ecosystems.