Food-web reorganization in an artificial reef revealed by flow-based indicators

Artificial-reef assessments often rely on abundance and biomass, but whether reef-associated differences extend to trophic pathways requires process-oriented indicators. We tested whether 2023 reef-control differences at Xiaoheishan were accompanied by coherent changes in community structure, trophic-resource use and Ecopath flows, and evaluated the Benthic Coupling Index (BCI) and Reef Fish Support Index (RFSI). Three reef and three adjacent control stations were sampled in March, June, August and November and integrated to characterize the annual ecological state. Reef-control differences in abundance and biomass reversed among seasons, whereas the reef area contained more small and intermediate consumers and higher biomass of reef-associated fishes. The sample-size-corrected standard ellipse area (SEAc) point estimate was larger in the reef assemblage (13.54 vs. 8.83 ‰ 2 ), although the 95% interval for the difference included zero; basal-resource profiles remained highly similar. The reef Ecopath model combined higher total living biomass and stronger benthic-detrital routing with lower total system throughput. BCI increased from 0.229 to 0.451 and retained separation under ±20% directional perturbation; RFSI increased from 0.544 to 0.595 but overlapped under ±10%, identifying reef-fish diet allocation as a key source of sensitivity. These results support local food-web reorganization within the reef-control system and show that matched Ecopath flow matrices can be summarized by two indicators with different sensitivities. Cross-system and interannual validation are needed before either index is used as a general management threshold; regional production and spillover were not evaluated.