title: Biodiversity mediates top-down control in eelgrass ecosystems: a global comparative-experimental approach.
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.
authors.affiliation: Virginia Institute of Marine Science, Gloucester Point, VA, 23062-1346, USA.|Tennenbaum Marine Observatories Network, Smithsonian Institution, Washington, D.C., 20013-7012, USA.
authors.forename: J Emmett
authors.initials: JE
authors.lastname: Duffy
authors.affiliation: Virginia Institute of Marine Science, Gloucester Point, VA, 23062-1346, USA.
authors.forename: Pamela L
authors.initials: PL
authors.lastname: Reynolds
authors.affiliation: Department of Biosciences, Environmental and Marine Biology, Åbo Akademi University, 20520, Åbo, Finland.
authors.forename: Christoffer
authors.initials: C
authors.lastname: Boström
authors.affiliation: Shoals Marine Laboratory, Cornell University, Portsmouth, NH, 03801, USA.
authors.forename: James A
authors.initials: JA
authors.lastname: Coyer
authors.affiliation: Département des sciences fondamentales & Québec-Océan, Université du Québec à Chicoutimi, Chicoutimi, QC, G7H 2B1, Canada.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Cusson
authors.affiliation: Centre for Ecological and Evolutionary Studies, University of Groningen, 9747 AG, Groningen, The Netherlands.
authors.forename: Serena
authors.initials: S
authors.lastname: Donadi
authors.affiliation: Florida Gulf Coast University, Fort Myers, FL, 33965, USA.
authors.forename: James G
authors.initials: JG
authors.lastname: Douglass
authors.affiliation: Department of Ecology, Environment and Plant Sciences, Stockholm University, 106 91, Stockholm, Sweden.
authors.forename: Johan S
authors.initials: JS
authors.lastname: Eklöf
authors.affiliation: Centro de Ciências do Mar do Algarve (CCMAR), University of Algarve, 8005 139, Faro, Portugal.
authors.forename: Aschwin H
authors.initials: AH
authors.lastname: Engelen
authors.affiliation: Centre for Ecological and Evolutionary Studies, University of Groningen, 9747 AG, Groningen, The Netherlands.
authors.forename: Britas Klemens
authors.initials: BK
authors.lastname: Eriksson
authors.affiliation: Department of Biosciences, University of Oslo, 0316, Oslo, Norway.
authors.forename: Stein
authors.initials: S
authors.lastname: Fredriksen
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30, Göteborg, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Gamfeldt
authors.affiliation: Tvärminne Zoological Station, University of Helsinki, 10900, Hanko, Finland.
authors.forename: Camilla
authors.initials: C
authors.lastname: Gustafsson
authors.affiliation: Faculty of Biosciences and Aquaculture, University of Nordland, 8049, Bodø, Norway.
authors.forename: Galice
authors.initials: G
authors.lastname: Hoarau
authors.affiliation: Fisheries Research Agency, 739-0452, Hiroshima, Japan.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Hori
authors.affiliation: Department of Biology, San Diego State University, San Diego, CA, 92182, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Hovel
authors.affiliation: School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, AK, 99775, USA.
authors.forename: Katrin
authors.initials: K
authors.lastname: Iken
authors.affiliation: Virginia Institute of Marine Science, Gloucester Point, VA, 23062-1346, USA.
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Lefcheck
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30, Göteborg, Sweden.
authors.forename: Per-Olav
authors.initials: PO
authors.lastname: Moksnes
authors.affiliation: Akkeshi Marine Station, Field Science Center for Northern Biosphere, Hokkaido University, Aikappu, Akkeshi, Hokkaido, 088-1113, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Nakaoka
authors.affiliation: Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
authors.forename: Mary I
authors.initials: MI
authors.lastname: O'Connor
authors.affiliation: Centre for Ecological and Evolutionary Studies, University of Groningen, 9747 AG, Groningen, The Netherlands.
authors.forename: Jeanine L
authors.initials: JL
authors.lastname: Olsen
authors.affiliation: Virginia Institute of Marine Science, Gloucester Point, VA, 23062-1346, USA.
authors.forename: J Paul
authors.initials: JP
authors.lastname: Richardson
authors.affiliation: Department of Biology, University of Washington, Seattle, WA, 98195, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Ruesink
authors.affiliation: Grice Marine Laboratory, College of Charleston, Charleston, SC, 29412, USA.
authors.forename: Erik E
authors.initials: EE
authors.lastname: Sotka
authors.affiliation: Department of Biosciences, University of Oslo, 0316, Oslo, Norway.
authors.forename: Jonas
authors.initials: J
authors.lastname: Thormar
authors.affiliation: Department of Evolution and Ecology, University of California, Davis, CA, 95616, USA.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Whalen
authors.affiliation: Department of Evolution and Ecology, University of California, Davis, CA, 95616, USA.
authors.forename: John J
authors.initials: JJ
authors.lastname: Stachowicz
mesh_terms: D000818:Animals; D044822:Biodiversity; D018533:Biomass; D003445:Crustacea; D005068:Eutrophication; D020387:Food Chain; D049851:Gastropoda; D005838:Genotype; D060434:Herbivory; D058086:Microalgae; D008954:Models, Biological; D011157:Population Dynamics; D035962:Zosteraceae / Q000235:genetics / Q000502:physiology*
keywords: Biodiversity-ecosystem functioning; bottom-up control; coordinated experiments; food webs; metabolic ecology; structural equation modelling; top-down control