Newly constructed regulation reservoirs experience dramatic seasonal environmental shifts, yet the temporal dynamics of their aquatic food webs remain poorly understood. In this study, we investigated the seasonal variations in fish community structure and trophic niches in Xianlin Reservoir (Zhejiang, China) using catch surveys and stable isotope analysis (δ13C and δ15N). Our results revealed that the fish assemblage was persistently dominated by the non-native fish Lepomis macrochirus and the native Xenocypris argentea. Community-wide isotopic metrics, calculated via SIBER, demonstrated pronounced seasonal plasticity in the trophic architecture. During winter, driven by limited basal resources, the community exhibited a “dietary expansion” strategy, resulting in the longest vertical food chain, the broadest core isotopic niche area (SEAc = 16.33), and the lowest trophic redundancy (indicated by the highest mean nearest neighbor distance). Conversely, the spring community displayed a highly compressed trophic structure characterized by dense species packing and maximum redundancy. These findings highlight that the reservoir food web exhibits a reduced functional buffering capacity during winter due to weak functional substitutability among high-trophic-level species. Given the ongoing community assembly in this newly constructed reservoir, the system is potentially more susceptible to seasonal environmental perturbations.
Zhong et al. (Thu,) studied this question.