Biodiversity mediates top–down control in eelgrass ecosystems: a global comparative‐experimental approach |
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| Authors: | J. Emmett Duffy,Pamela L. Reynolds,Christoffer Boström,James A. Coyer,Mathieu Cusson,Serena Donadi,James G. Douglass,Johan S. Eklöf,Aschwin H. Engelen,Britas Klemens Eriksson,Stein Fredriksen,Lars Gamfeldt,Camilla Gustafsson,Galice Hoarau,Masakazu Hori,Kevin Hovel,Katrin Iken,Jonathan S. Lefcheck,Per‐Olav Moksnes,Masahiro Nakaoka,Mary I. O'Connor,Jeanine L. Olsen,J. Paul Richardson,Jennifer L. Ruesink,Erik E. Sotka,Jonas Thormar,Matthew A. Whalen,John J. Stachowicz |
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| Affiliation: | 1. Virginia Institute of Marine Science, Gloucester Point, VA, USA;2. Tennenbaum Marine Observatories Network, Smithsonian Institution, Washington, D.C., USA;3. Department of Biosciences, Environmental and Marine Biology, ?bo Akademi University, ?bo, Finland;4. Shoals Marine Laboratory, Cornell University, Portsmouth, NH, USA;5. Département des sciences fondamentales & Québec‐Océan, Université du Québec à Chicoutimi, Chicoutimi, QC, Canada;6. Centre for Ecological and Evolutionary Studies, University of Groningen, Groningen, The Netherlands;7. Florida Gulf Coast University, Fort Myers, FL, USA;8. Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden;9. Centro de Ciências do Mar do Algarve (CCMAR), University of Algarve, Faro, Portugal;10. Department of Biosciences, University of Oslo, Oslo, Norway;11. Department of Biological and Environmental Sciences, University of Gothenburg, G?teborg, Sweden;12. Tv?rminne Zoological Station, University of Helsinki, Hanko, Finland;13. Faculty of Biosciences and Aquaculture, University of Nordland, Bod?, Norway;14. Fisheries Research Agency, Hiroshima, Japan;15. Department of Biology, San Diego State University, San Diego, CA, USA;16. School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, AK, USA;17. Akkeshi Marine Station, Field Science Center for Northern Biosphere, Hokkaido University, Akkeshi, Hokkaido, Japan;18. Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada;19. Department of Biology, University of Washington, Seattle, WA, USA;20. Grice Marine Laboratory, College of Charleston, Charleston, SC, USA;21. Department of Evolution and Ecology, University of California, Davis, CA, USA |
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| Abstract: | Nutrient pollution and reduced grazing each can stimulate algal blooms as shown by numerous experiments. But because experiments rarely incorporate natural variation in environmental factors and biodiversity, conditions determining the relative strength of bottom–up and top–down forcing remain unresolved. We factorially added nutrients and reduced grazing at 15 sites across the range of the marine foundation species eelgrass (Zostera marina) to quantify how top–down and bottom–up control interact with natural gradients in biodiversity and environmental forcing. Experiments confirmed modest top–down control of algae, whereas fertilisation had no general effect. Unexpectedly, grazer and algal biomass were better predicted by cross‐site variation in grazer and eelgrass diversity than by global environmental gradients. Moreover, these large‐scale patterns corresponded strikingly with prior small‐scale experiments. Our results link global and local evidence that biodiversity and top–down control strongly influence functioning of threatened seagrass ecosystems, and suggest that biodiversity is comparably important to global change stressors. |
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| Keywords: | Biodiversity‐ecosystem functioning bottom– up control coordinated experiments food webs metabolic ecology structural equation modelling top– down control |
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