A review in intertidal flats of the Yangtze Estuary over the past 25 years: shifting research focus and varying macrobenthos richness

The Yangtze Estuary, the largest estuary in China's subtropical zone, harbors considerable biodiversity. Nevertheless, comprehensive analysis of long-term trends in species richness within this region have been limited. In this study, all relevant peer-reviewed papers focused on the macrobenthos of the intertidal flats of the Yangtze Estuary from the past 25 years were reviewed. We performed a keyword co-occurrence analysis to track evolving research priorities and compiled species inventories for reclassification and identification. Keyword co-occurrence analysis revealed that early studies established a foundational understanding of macrobenthos communities, while subsequent research shifted toward assessing the impacts of human activities on community health. A total of 254 taxa from 9 phyla were recorded, with Arthropoda (n = 98) being the most common taxa (but their proportion decreased over time), followed by Mollusca (n = 80) and Annelida (n = 50), at an approximate ratio of 4:3:2. Among the 44 common species listed, 10 were annelids, 11 were mollusks, 22 were arthropods and 1 was nemertean. The total species richness generally showed an increasing trend toward stabilization temporally. Macrobenthos richness and community structure varied spatially: South bank of the Yangtze River Estuary, Jiuduansha, and Chongming Island supported the higher species diversity, whereas Changxing and Hengsha Island and Deep Water Navigation Channel exhibited lower. Overall, our findings underscored that spatial heterogeneity exerted a stronger influence on macrobenthos community structure than temporal change. Based on these results, we proposed recommendations for future research to inform estuarine conservation and resource management strategies.