Plankton Enrichment Effects of Novel Artificial Reefs in the Upper Yangtze River

A novel artificial reef with attached ecological rods has been widely applied in the waterway regulation project in the Chongqing section of the upper Yangtze River. In this study, a scaled-down prototype of the artificial reef with ecological rods was placed in an artificial lake, and the temporal changes in planktonic biodiversity and community structure were analyzed to assess its enrichment effect on plankton. The results reveal significant differences in the planktonic community structure between the artificial lake and the ecological rods, with substrate-included variations being more pronounced than those resulting from enrichment duration. Furthermore, the planktonic community within the ecological rods exhibited significant changes over the 5-15 days enrichment period. High-throughput sequencing results show that the eukaryotic biodiversity index in the ecological rods was lower than in the lake and gradually decreased over time, while the prokaryotic biodiversity index showed the opposite trend. In the artificial lake, the dominant eukaryotic groups were Chlorophyta (46.6%-53.2%) and Cryptophyta (19.7%-26.6%), whereas in the ecological rods, the relative abundance of Chlorophyta (42.3%-89.4%) increased progressively over time, while Cryptophyta were nearly absent. For prokaryotes, the artificial lake was dominated by Gammaproteobacteria (27.2%-28.4%), Actinobacteria (19.3%-21.5%), and Bacteroidia (15.9%-17.6%). In contrast, in the ecological rods, the relative abundance of Alphaproteobacteria (14.6%-24.0%) and Gammaproteobacteria (13.5%-28.0%) decreased, while Cyanobacteriia (14.0%-34.2%) became more dominant over time. Dissolved oxygen levels gradually declined, while total nitrogen and chlorophyll concentrations peaked on day 10 of enrichment, serving as the primary factors influencing planktonic community structure. The polyurethane sponge material in the ecological rods exhibited 95% porosity and a specific surface area of 27.41 m²·g^-1, which, compared to other artificial reef materials, facilitates plankton attachment due to its high porosity and large surface area. The findings provide a theoretical foundation for the design and construction of artificial reefs and for habitat restoration in the upper Yangtze River.