Spatial-Temporal Dynamics and Co-Occurrence Networks of Zooplankton Community Structure in a Large Shallow Reservoir...

Zooplankton are sensitive indicators of ecological change, but their community reorganization under early-phase restoration remains unclear. This study aims to reveal how their diversity, standing stock, and co-occurrence networks respond to early-phase restoration and identifies key environmental drivers, offering novel insights into restoration-plankton interplay. Shilianghe Reservoir, as the largest reservoir in Jiangsu Province, represents a typical case of restoration in the Huai River Basin that offers transferable insights for numerous eutrophic reservoirs. The study comprised eight surveys representing two annual cycles (July 2021-May 2022 and April 2023-January 2024). The 2023 sampling cycle showed lower zooplankton density and biomass but higher α-diversity than the 2021 sampling cycle. Co-occurrence network density and the size of the largest connected component decreased in spring and summer of the 2023 sampling cycle, suggesting community reorganization. Inflow tributaries supported the highest species richness and standing stock but showed looser interspecific associations. PERMANOVA analysis indicated that season explained the largest proportion of community variation, followed by sampling year and region. Environmental variables including DO, WT, Cond and TN significantly correlated with zooplankton community structure. Zooplankton community reorganization was characterized by reduced standing stock, increased diversity, and altered co-occurrence patterns, providing a mechanistic framework for using zooplankton as bioindicators in reservoir restoration assessments.