title: Marine ecosystem connectivity mediated by migrant-resident interactions and the concomitant cross-system flux of lipids.
abstract: Accumulating research argues that migrants influence the functioning and productivity of local habitats and ecosystems along migration routes and potentially drive cross-system energy fluxes of considerable magnitude, yet empirical documentation of local ecological effects and descriptions of the underlying mechanisms are surprisingly rare. In this study, we discovered migrant-resident interactions and substantial cross-system lipid transportation in the transition zone between the Baltic Sea and the North Sea where a resident cod population (predators) was found to interact with a herring population (prey) on a seasonal basis. We traced the lipids, using fatty acid trophic markers (FATM), from the herring feeding grounds in the North Sea to the cod livers in the Western Baltic Sea. Time series analysis of population dynamics indicated that population-level production of cod is positively affected by the herring subsidies. However, the underlying mechanisms were more complicated than anticipated. During the herring season, large cod received most of its dietary lipids from the herring, whereas smaller cod were prevented from accessing the lipid pool due to a mismatch in predator-prey size ratio. Furthermore, while the herring were extremely rich in bulk energy, they were surprisingly poor in a specific functional fatty acid. Hence, our study was the first to illustrate how the magnitude cross-system fluxes of subsidies in migrant-resident systems are potentially constrained by the size structure of the resident predator population and the nutritional quality of the migrants.
authors: Department of Biology - Aquatic Ecology Lund University Ecology Building SE-223 62 Lund Sweden; National Institute for Aquatic resources - Section for Marine Living Resources Technical University of Denmark Jægersborgs alle 1DK-2920 Charlottenlund Denmark.
authors: Mikael
authors: M
authors: van Deurs
authors: Department of Biology - Aquatic Ecology Lund University Ecology Building SE-223 62 Lund Sweden.
authors: Anders
authors: A
authors: Persson
authors: National Institute for Aquatic resources - Section for Marine Living Resources Technical University of Denmark Jægersborgs alle 1 DK-2920 Charlottenlund Denmark.
authors: Martin
authors: M
authors: Lindegren
authors: National Food Institute Technical University of Denmark Søltofts plads Building 221 DK-2800 Kgs. Lyngby Denmark.
authors: Charlotte
authors: C
authors: Jacobsen
authors: National Institute for Aquatic resources - Section for Marine Living Resources Technical University of Denmark Jægersborgs alle 1 DK-2920 Charlottenlund Denmark.
authors: Stefan
authors: S
authors: Neuenfeldt
authors: Department of Biology - Theoretical Ecology Group and Hjort Centre for Marine Ecosystem Dynamics University of Bergen N-5020 Bergen Norway.
authors: Christian
authors: C
authors: Jørgensen
authors: Department of Biology - Aquatic Ecology Lund University Ecology Building SE-223 62 Lund Sweden; Department of Environmental and Life Sciences - Biology Karlstad University SE-651 88 Karlstad Sweden.
authors: P Anders
authors: PA
authors: Nilsson
keywords: Arachidonic acid; Baltic Sea; Clupea harengus; FATM; Gadus morhua; dietary fatty acids; food quality; meta‐ecosystem; migration; nutritional quality; predator–prey interactions; resource subsidies; trophic tracers