Trophic Cascades in a Formerly Cod-Dominated Ecosystem

  title={Trophic Cascades in a Formerly Cod-Dominated Ecosystem},
  author={Kenneth T. Frank and Brian Petrie and Jae S. Choi and William C. Leggett},
  pages={1621 - 1623}
Removal of top predators from ecosystems can result in cascading effects through the trophic levels below, completely restructuring the food web. Cascades have been observed in small-scale or simple food webs, but not in large, complex, open-ocean ecosystems. Using data spanning many decades from a once cod-dominated northwest Atlantic ecosystem, we demonstrate a trophic cascade in a large marine ecosystem. Several cod stocks in other geographic areas have also collapsed without recovery… 
Trophic cascades promote threshold-like shifts in pelagic marine ecosystems
An ecological threshold is identified, corresponding to a planktivore abundance of ≈17 × 1010 individuals, that separates 2 ecosystem configurations in which zooplankton dynamics are driven by either hydroclimatic forces or predation pressure, and the current strong regulation by sprat of the feeding resources for larval cod may hinder cod recovery and the return of the ecosystem to a prior state.
Evaluating trophic cascades as drivers of regime shifts in different ocean ecosystems
In ecosystems that are strongly structured by predation, reducing top predator abundance can alter several lower trophic levels—a process known as a trophic cascade. A persistent trophic cascade also
Trophic and functional cascades in tropical versus temperate aquatic microcosms
Food web changes in trophic structure and ecosystem functioning following biomass removal of top predators in representative temperate and tropical rock pool communities that contained similar assemblages of zooplankton and benthic invertebrates show changes in structural and functioning properties and increase in variability of ecosystem processes.
Multi-level trophic cascades in a heavily exploited open marine ecosystem
This work shows for the first time a four-level community-wide trophic cascade in the open Baltic Sea, and suggests that in order to dampen the occasionally harmful algal blooms of the Baltic, effort should be addressed not only to control anthropogenic nutrient inputs but also to preserve structure and functioning of higher Trophic levels.
A trophic cascade triggers collapse of a salt-marsh ecosystem with intensive recreational fishing.
It is found that the localized depletion of top predators at sites accessible to recreational anglers has triggered the proliferation of herbivorous crabs, which in turn results in runaway consumption of marsh vegetation, suggesting that overfishing may be a general mechanism underlying the consumer-driven die-off of salt marshes spreading throughout the western Atlantic.
Damped trophic cascades driven by fishing in model marine ecosystems
A novel size- and trait-based model is used to explore how marine ecosystems might react to perturbations from different types of fishing pressure, and shows that fishing does not change the overall slope of the size spectrum, but depletes the largest individuals and induces trophic cascades.
Cascading Effects of the Loss of Apex Predatory Sharks from a Coastal Ocean
Impacts of chronic overfishing are evident in population depletions worldwide, yet indirect ecosystem effects induced by predator removal from oceanic food webs remain unpredictable. As abundances of
Trophic cascades triggered by overfishing reveal possible mechanisms of ecosystem regime shifts
Two major shifts were detected, the first related to a depletion of marine predators and the second to an outburst of the alien comb jelly Mnemiopsis leidyi; both shifts were triggered by intense fishing resulting in system-wide trophic cascades.
Changing Ecosystem Dynamics in the Laurentian Great Lakes: Bottom-Up and Top-Down Regulation
Understanding the relative importance of top-down and bottom-up regulation of ecosystem structure is a fundamental ecological question, with implications for fisheries and water-quality management.


Trophic cascades revealed in diverse ecosystems.
A cross-ecosystem comparison of the strength of trophic cascades
Although trophic cascades (indirect effects of predators on plants via herbivores) occur in a wide variety of food webs, the magnitudes of their effects are often quite variable. We compared the
Fishing down marine food webs
The mean trophic level of the species groups reported in Food and Agricultural Organization global fisheries statistics declined from 1950 to 1994, and results indicate that present exploitation patterns are unsustainable.
The premise is that true trophic cascades in the community sense are a relatively unusual sort of food web mechanics, and evidence is that these cascades are restricted to fairly low-diversity places where great influence can issue from one or a few species.
When is a trophic cascade a trophic cascade?
Eutrophication, Fisheries, and Consumer-Resource Dynamics in Marine Pelagic Ecosystems.
  • Micheli
  • Environmental Science
  • 1999
Meta-analyses of 47 marine mesocosm experiments manipulating nutrients and consumers revealed that nutrients generally enhance phytoplankton biomass and carnivores depress herbivore biomass, however, resource and consumer effects attenuate through marine pelagic food webs, resulting in a weak coupling between phy Topolankton and herbivores.
Catastrophic shifts in ecosystems
Recent studies show that a loss of resilience usually paves the way for a switch to an alternative state, which suggests that strategies for sustainable management of such ecosystems should focus on maintaining resilience.
Impacts of fisheries on plankton community structure
There has been much debate on the extent to which resource availability (bottom-up) versus predation pressure from fish (top-down) modulates the dynamics of plankton in marine systems.
Historical Overfishing and the Recent Collapse of Coastal Ecosystems
Ecological extinction caused by overfishing precedes all other pervasive human disturbance to coastal ecosystems, including pollution, degradation of water quality, and anthropogenic climate change.
Transition to an alternate state in a continental shelf ecosystem
This analysis of a fishery-independent, long-term, standardized database collected on the eastern Scotian Shelf off Nova Scotia revealed that during the past four decades, coherent, community-level reductions in body size, biomass, and physiological condition have occurred in the resident demersal fish species.