Author(s): Chen Zhang; Ruolan Yu

Linked Author(s): Chen Zhang

Keywords: Eutrophication; Trophic control; Freshwater food web

Abstract: Eutrophication drives algal blooms and loss of water clarity in shallow water ecosystems. Biomanipulation of fish and macrophytes is a practical restoration strategy, but quantitative evidence for zooplankton group - specific responses remains limited. We combined an in situ mesocosm experiment manipulating planktivorous fish and macrophytes with scenario-based simulations using a multi-species zooplankton module, which explicitly represents rotifers, cladocerans, and copepods. The model was calibrated and validated with observations from the temperate mesocosm system, including temperature, dissolved oxygen (DO), total nitrogen (TN), total phosphorus (TP), chlorophyll a (Chla), macrophytes, zooplankton, and fish, and evaluated against mesocosm patterns. Model performance against the mesocosm observations was generally good to very good (NSE ≥ 0.71; R2 ≥ 0.6). Both observations and simulations showed strong seasonal effects with zooplankton group-specific responses. In spring and summer, reducing fish increased all three zooplankton groups, especially rotifers, and decreased phytoplankton. In autumn, rotifers increas ed, but cladocerans and copepods declined under fish removal, accompanied by higher phytoplankton. Increasing macrophyte coverage consistently promoted all zooplankton groups and suppressed phytoplankton across seasons, with particularly strong phytoplankton reductions in autumn. Overall, our results support a fish –zooplankton– macrophyte–phytoplankton cascade and suggest that macrophyte reestablishment and spring-summer removal of zooplanktivorous fish are effective methods to mitigate eutrophication in shallow water ecosystems.

DOI: https://doi.org/10.64697/iahr.proc.ise2026.abs.235

Year: 2026