Warming increases trophic cascade strength in an aquatic food chain

Trophic cascades play a central role in shaping ecosystems, yet it is unclear how their strength responds to warming. Because species' demographics and trophic interaction strengths are temperature sensitive, climate change is expected to alter cascade strengths, with potentially widespread ecological consequences. We experimentally tested how temperature affects trophic cascade strength by manipulating the presence of the predator Hydra oligactis and tracking the abundances of its prey, Ceriodaphnia reticulata, and primary producer, Ankistrodesmus falcatus, across a temperature gradient. To uncover the mechanisms driving these changes, we complemented the experiment with mathematical models fit to the population dynamics, providing novel insight into why trophic cascade strength changes with warming. We predicted that warming would strengthen trophic cascades by increasing direct consumer-resource interaction strengths. Our results supported this prediction, and we also found that higher temperatures amplified transient population fluctuations, driven by the combined temperature dependence of nearly all the model parameters. Our findings show that climate warming can strengthen trophic cascades, destabilize population dynamics and magnify the ecological impacts of predator loss through complex, temperature-dependent changes in species interactions and demographics.