Nutrient reduction and climate change cause a potential shift from pelagic to benthic pathways in a eutrophic marine ecosystem

Authors

  • Martin Lindegren,

    Corresponding author
    1. National Institute of Aquatic Resources, Technical University of Denmark, Charlottenlund, Denmark
    • Scripps Institution of Oceanography, University of California, La Jolla, USA
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  • Thorsten Blenckner,

    1. Baltic Nest Institute, Stockholm Resilience Centre, Stockholm University, Stockholm, Sweden
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  • Nils C. Stenseth

    1. Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, Oslo, Norway
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Correspondence: Dr. Martin Lindegren, Scripps Institution of Oceanography, University of California, 9500 Gilman Drive, La Jolla, CA 92093-0218, USA, tel. +1 858 534 9252, fax +1 858 534 2997, e-mail: mlindegren@ucsd.edu

Abstract

The degree to which marine ecosystems may support the pelagic or benthic food chain has been shown to vary across natural and anthropogenic gradients for e.g., in temperature and nutrient availability. Moreover, such external forcing may not only affect the flux of organic matter but could trigger large and abrupt changes, i.e., trophic cascades and ecological regime shifts, which once having occurred may prove potentially irreversible. In this study, we investigate the state and regulatory pathways of the Kattegat; a eutrophied and heavily exploited marine ecosystem, specifically testing for the occurrence of regime shifts and the relative importance of multiple drivers, e.g., climate change, eutrophication and commercial fishing on ecosystem dynamics and trophic pathways. Using multivariate statistics and nonlinear regression on a comprehensive data set, covering abiotic factors and biotic variables across all trophic levels, we here propose a potential regime shift from pelagic to benthic regulatory pathways; a possible first sign of recovery from eutrophication likely triggered by drastic nutrient reductions (involving both nitrogen and phosphorus), in combination with climate-driven changes in local environmental conditions (e.g., temperature and oxygen concentrations).

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