title: Predator transitory spillover induces trophic cascades in ecological sinks.
abstract: Understanding the effects of cross-system fluxes is fundamental in ecosystem ecology and biological conservation. Source-sink dynamics and spillover processes may link adjacent ecosystems by movement of organisms across system boundaries. However, effects of temporal variability in these cross-system fluxes on a whole marine ecosystem structure have not yet been presented. Here we show, using 35 y of multitrophic data series from the Baltic Sea, that transitory spillover of the top-predator cod from its main distribution area produces cascading effects in the whole food web of an adjacent and semi-isolated ecosystem. At varying population size, cod expand/contract their distribution range and invade/retreat from the neighboring Gulf of Riga, thereby affecting the local prey population of herring and, indirectly, zooplankton and phytoplankton via top-down control. The Gulf of Riga can be considered for cod a "true sink" habitat, where in the absence of immigration from the source areas of the central Baltic Sea the cod population goes extinct due to the absence of suitable spawning grounds. Our results add a metaecosystem perspective to the ongoing intense scientific debate on the key role of top predators in structuring natural systems. The integration of regional and local processes is central to predict species and ecosystem responses to future climate changes and ongoing anthropogenic disturbances.
authors.affiliation: Swedish University of Agricultural Sciences, Department of Aquatic Resources, Institute of Marine Research, 54330 Lysekil, Sweden. michele.casini@slu.se
authors.forename: Michele
authors.initials: M
authors.lastname: Casini
authors.forename: Thorsten
authors.initials: T
authors.lastname: Blenckner
authors.forename: Christian
authors.initials: C
authors.lastname: Möllmann
authors.forename: Anna
authors.initials: A
authors.lastname: Gårdmark
authors.forename: Martin
authors.initials: M
authors.lastname: Lindegren
authors.forename: Marcos
authors.initials: M
authors.lastname: Llope
authors.forename: Georgs
authors.initials: G
authors.lastname: Kornilovs
authors.forename: Maris
authors.initials: M
authors.lastname: Plikshs
authors.forename: Nils Christian
authors.initials: NC
authors.lastname: Stenseth
mesh_terms: D000818:Animals; D057231:Climate Change; D004463:Ecology; D017753:Ecosystem; D020387:Food Chain; D048389:Gadus morhua / Q000502:physiology*; D015233:Models, Statistical; D009792:Oceans and Seas; D011156:Population Density; D011157:Population Dynamics; D011235:Predatory Behavior / Q000502:physiology*; D015048:Zooplankton / Q000502:physiology