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Updated: May 23, 2026
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Published on: March 12, 2013
Predator transitory spillover induces trophic cascades in ecological sinks
Michele Casini1, Thorsten Blenckner, Christian Möllmann
1Swedish University of Agricultural Sciences, Department of Aquatic Resources, Institute of Marine Research, 54330 Lysekil, Sweden. michele.casini@slu.se
Summary
Top predator cod spillover into the Gulf of Riga creates cascading food web effects. This highlights the importance of cross-system fluxes for marine ecosystem structure and conservation.
Area of Science:
- Marine ecology
- Ecosystem dynamics
- Metaecosystem science
Background:
- Cross-system fluxes, including source-sink dynamics and spillover, connect adjacent ecosystems through organism movement.
- Temporal variability in these fluxes can significantly impact marine ecosystem structure, but this remains understudied.
- Top predators play a crucial role in structuring food webs, influencing lower trophic levels.
Purpose of the Study:
- To investigate the effects of temporal variability in cross-system fluxes on a marine ecosystem.
- To analyze the cascading effects of top-predator (cod) spillover on the food web of an adjacent ecosystem (Gulf of Riga).
- To understand the role of a semi-isolated ecosystem as a 'sink' habitat for a mobile predator.
Main Methods:
- Analysis of 35 years of multitrophic data from the Baltic Sea.
- Tracking cod distribution range shifts and population dynamics.
- Assessing the impact of cod presence on herring populations and, indirectly, on zooplankton and phytoplankton.
Main Results:
- Transitory spillover of Baltic Sea cod into the Gulf of Riga caused cascading effects throughout the local food web.
- Cod's expanding/contracting distribution range influenced herring populations, leading to indirect top-down control on zooplankton and phytoplankton.
- The Gulf of Riga functions as a 'sink' habitat for cod, with local populations unable to sustain without immigration due to unsuitable spawning grounds.
Conclusions:
- Temporal variability in cross-system fluxes, specifically cod spillover, significantly structures adjacent marine ecosystems.
- Top-down control exerted by mobile predators is a key mechanism linking regional and local ecosystem processes.
- Integrating metaecosystem perspectives is crucial for predicting ecosystem responses to climate change and anthropogenic disturbances.
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