Warming, eutrophication, and predator loss amplify subsidies between aquatic and terrestrial ecosystems

Authors

  • Hamish S. Greig,

    Corresponding author
    1. Department of Forest Sciences, University of British Columbia, Vancouver, BC, Canada
    • Biodiversity Research Centre and Zoology Department, University of British Columbia, Vancouver, BC, Canada
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  • Pavel Kratina,

    1. Biodiversity Research Centre and Zoology Department, University of British Columbia, Vancouver, BC, Canada
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  • Patrick L. Thompson,

    1. Biodiversity Research Centre and Zoology Department, University of British Columbia, Vancouver, BC, Canada
    2. Department of Biology, McGill University, Montreal, QC, Canada
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  • Wendy J. Palen,

    1. Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada
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  • John S. Richardson,

    1. Biodiversity Research Centre and Zoology Department, University of British Columbia, Vancouver, BC, Canada
    2. Department of Forest Sciences, University of British Columbia, Vancouver, BC, Canada
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  • Jonathan B. Shurin

    1. Biodiversity Research Centre and Zoology Department, University of British Columbia, Vancouver, BC, Canada
    2. Section of Ecology, Behavior and Evolution, UC-San Diego, La Jolla, CA, USA
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  • Hamish S. Greig and Pavel Kratina contributed equally to this work.

Correspondence: Hamish S. Greig, School of Biological Sciences, University of Canterbury, Christchurch 8140, New Zealand, tel. + 64 3 364 2500, fax + 64 3 364 2590, e-mail: hamish.greig@canterbury.ac.nz

Abstract

The exchange of organisms and energy among ecosystems has major impacts on food web structure and dynamics, yet little is known about how climate warming combines with other pervasive anthropogenic perturbations to affect such exchanges. We used an outdoor freshwater mesocosm experiment to investigate the interactive effects of warming, eutrophication, and changes in top predators on the flux of biomass between aquatic and terrestrial ecosystems. We demonstrated that predatory fish decoupled aquatic and terrestrial ecosystems by reducing the emergence of aquatic organisms and suppressing the decomposition of terrestrial plant detritus. In contrast, warming and nutrients enhanced cross-ecosystem exchanges by increasing emergence and decomposition, and these effects were strongest in the absence of predators. Furthermore, we found that warming advanced while predators delayed the phenology of insect emergence. Our results demonstrate that anthropogenic perturbations may extend well beyond ecosystem boundaries by influencing cross-ecosystem subsidies. We find that these changes are sufficient to substantially impact recipient communities and potentially alter the carbon balance between aquatic and terrestrial ecosystems and the atmosphere.

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