Responses of macrobenthic communities and ecological quality along land-derived pollution gradients in Gyeonggi Bay

Marine ecosystems in semi-enclosed Gyeonggi Bay (Yellow Sea, Korea) were surveyed at 23 stations arrayed along four discharge transects to evaluate how sediment texture and contaminants influence macrobenthic communities. A total of 186 species were recorded, yet richness tends to decrease at innermost stations. Highly simplified communities were dominated by two opportunistic species, Capitella capitata and Heteromastus filiformis. Community composition was strongly influenced by sorting and contaminants, particularly copper, cadmium, total organic carbon, and polycyclic aromatic hydrocarbons rather than distance from potential pollution sources. Diversity-based metrics tracked organic enrichment, whereas tolerance-weighted scores aligned with persistent toxic substances, revealing the risk of misclassification when a single index is used. Macrobenthic communities serve as indicators of pollution and inform integrated coastal monitoring strategies. Integrating complementary indices with chemical data therefore provides a clearer "fingerprint" of environmental stress and a stronger basis for station-scale management of patchy pollution in coastal embayment.