Measurement
During the course of the experiment, phytoplankton biomass (measured as Chl-a concentration) was quantified at a weekly basis to track phytoplankton response and calculate the trophic cascade strength. We also measured the net production at each trophic level for estimating energy transfer efficiencies. Specifically, primary production (\(P_{\text{phy}}\)) was measured via the light-dark bottles method at the end of the experiment (Devlin et al. 2016). Zooplankton production (\(P_{\text{zoo}}\)) was estimated based on changes in the body size and egg production for each taxon from the third week onwards. Predator production (\(P_{\text{shr}}\)) was estimated as the increase rate of shrimp biomass throughout the experiment (Dickman et al.2008). Production at all trophic levels were measured in the unit of C L-1 day -1 (see details in SI Appendix 1 ).
Total nitrogen (TN) and total phosphorus (TP) concentrations in waters were monitored weekly, and elemental composition of each trophic level were also measured at the end of the experiment to assess the stochiometric responses of food webs. Due to practical reasons, however, for zooplankton species we only measured elemental composition of species D. magna and S. dorrii (see details in SI Appendix 1 ).