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 ).