Comparative effects of carp polyculture on phosphorus migration and water quality with a focus on Xenocypris microlepis integration

This study investigated how polyculture of Xenocypris microlepis with silver carp and bighead carp affects water quality and phosphorus transformation. Compared to controls, both polyculture and silver-bighead carp systems showed elevated nitrogen and phosphorus levels in the water body. However, the polyculture system maintained significantly lower TN and TP concentrations than the silver-bighead carp system. Sediment TP in polyculture systems was significantly lower ( P < 0.05) than in control and silver carp-only systems. Specifically, iron-bound phosphorus (Fe-P) and labile organic phosphorus fractions (fulvic-P, HCl-P, NaHCO 3 -P) decreased consistently in polyculture, while other groups exhibited fluctuating patterns. These results demonstrate that the tri-species polyculture enhances algal control through accelerated phosphorus cycling, improved biological phosphorus removal, and simultaneous reduction of aqueous and sedimentary phosphorus.These findings provide a scientific basisfor using carp polyculture in eutrophic water remediation.