Homogenization and functional simplification of zooplankton in reservoirs connected by water transfer

Abstract Water transfer projects between river basins have been globally adopted as strategies to mitigate water scarcity, especially in semi-arid regions. Although their socioeconomic benefits are widely recognized, the ecological effects of these interventions on aquatic ecosystems remain poorly understood. This study investigated how artificial connectivity between reservoirs influences the taxonomic and functional structure of zooplankton communities. A total of six reservoirs with different levels of connectivity were analyzed, classified as either recipients or nonrecipients of exogenous water. Taxonomic structure was assessed through species abundance and Hill numbers to estimate taxonomic richness, evenness, and dominance. Functional structure was analyzed using RLQ analysis, integrating biological traits and environmental data. The results revealed significant differences in zooplankton composition between groups of reservoirs. Recipient environments showed higher abundance of rotifers with generalist traits, while cladocerans and copepods were more predominant in nonrecipient environments. Artificial connectivity promoted functional homogenization, indicating a loss of ecological strategy diversity. These changes may compromise the balance of trophic networks, reduce the ecological resilience of aquatic systems, and affect essential ecosystem services such as phytoplankton biomass control and nutrient cycling. The findings highlight the need to account for ecological impacts in large-scale hydrological planning.