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Research article2015Peer reviewedOpen access

Biodiversity mediates top-down control in eelgrass ecosystems: a global comparative-experimental approach

Duffy JE, Reynolds PL, Bostrom C, Coyer JA, Cusson M, Donadi S, Douglass JG, Eklof JS, Engelen AH, Eriksson BK, Fredriksen S, Gamfeldt L, Gustafsson C, Hoarau G, Hori M, Hovel K, Iken K, Lefcheck JS, Moksnes PO, Nakaoka M, O'Connor MI, Olsen JL, Richardson JP, Ruesink JL, Sotka EE, Thormar J, Whalen MA, Stachowicz JJ

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.

Keywords

2015,biodiversity-ecosystem functioning,bottom,coordinated experiments,down control,ecology letters,food webs,metabolic ecology,structural equation modelling,top,up control

Published in

Ecology Letters
2015, Volume: 18, number: 7, pages: 696--705

      UKÄ Subject classification

      Ecology

      Publication identifier

      DOI: https://doi.org/10.1111/ele.12448

      Permanent link to this page (URI)

      https://res.slu.se/id/publ/88511