Abstract: To better understand the effects of seasonal hypoxia on macrobenthic communities in Yangtze Estuary, 4 surveys were carried out during summer from 2016 to 2019. Results showed that the lowest bottom-water dissolved oxygen (DO) was 1.51 mg/L, and the bottom-water hypoxia appeared in the Yangtze Estuary in summer from 2016 to 2019. There were significant differences in the species number, abundance, biomass and community structure of macrobenthos between hypoxic zone and non-hypoxic zone. Polychaetes showed greater tolerance to hypoxia，and were the dominant group in hypoxic zone. Mediomastus sp. and Lumbrinereis sp. were the main dominant species in hypoxic zone. Mollusks, crustaceans, and echinoderms showed the opposite trend to polychaetes, and crustaceans showed poor tolerance to hypoxia. Based on the MDS analysis, the community composition of macrobenthos between hypoxic zone and non-hypoxic zone was significantly different. CCA analysis showed that community structure of macrobenthos was influenced by the bottom-water hypoxia in Yangtze Estuary during summer.

Key words: macrobenthos, community structure, Yangtze Estuary, hypoxia, ecological effect