Predator mass mortality events restructure food webs through trophic decoupling.

Area of Science:

• Ecology
• Environmental Science
• Conservation Biology

Background:

• Predators are crucial for ecosystem structure, but global predator loss is increasing.
• Predator mass-mortality events (MMEs) are large-scale die-offs, poorly understood in their immediate ecological impacts.
• Existing studies on predator removal may not fully capture MME effects due to in-situ decomposition and resource pulses.

Purpose of the Study:

• To experimentally investigate the immediate ecological impacts of MMEs in freshwater lake food webs.
• To differentiate MME effects from simple predator removals or resource pulses.
• To understand how MMEs influence ecosystem dynamics and trophic interactions.

Main Methods:

• Experimental induction of MMEs in controlled, tritrophic freshwater lake food webs.
• Monitoring of consumer and producer community responses.
• Analysis of biomass dynamics and trophic interactions.

Main Results:

• MMEs promoted diverse consumer and producer communities by reducing top-down control and increasing bottom-up effects from decomposition.
• Enhanced primary production following MMEs counteracted consumer community responses.
• MMEs resulted in biomass dynamics resembling undisturbed systems, indicating they can be cryptic disturbances.
• Trophic decoupling occurred, with lost indirect predator benefits manifesting as direct bottom-up stimulation of primary production.

Conclusions:

• MMEs create distinct ecological signatures, differing from predator removals or resource pulses alone.
• The study demonstrates the feasibility of predicting novel ecological dynamics driven by MMEs in the context of global change.
• MMEs can lead to trophic decoupling and altered food web functioning, with potential long-term consequences for ecosystem stability.