Related Experiment Videos
Biodiversity mediates top-down control in eelgrass ecosystems: a global comparative-experimental approach.
J Emmett Duffy1,2, Pamela L Reynolds1, Christoffer Boström3
1Virginia Institute of Marine Science, Gloucester Point, VA, 23062-1346, USA.
Ecology Letters
|May 19, 2015
Summary
Biodiversity and top-down control, not nutrient pollution, significantly impact seagrass ecosystems. Eelgrass and grazer diversity, rather than global factors, better predict algal and grazer biomass in these vital marine habitats.
Area of Science:
- Marine ecology
- Ecosystem functioning
- Seagrass ecosystems
Background:
- Nutrient pollution and reduced grazing are known to cause algal blooms.
- Previous experiments often lack natural environmental variation and biodiversity, leaving the balance of top-down and bottom-up control unresolved.
Purpose of the Study:
- To investigate how top-down (grazing) and bottom-up (nutrient) controls interact with natural biodiversity and environmental gradients.
- To quantify the relative importance of these factors on seagrass ecosystem functioning across the range of eelgrass (Zostera marina).
Main Methods:
- Factorial addition of nutrients and reduction of grazing pressure at 15 diverse sites.
- Assessment of interactions between biodiversity, environmental factors, and ecosystem responses.
Main Results:
- Grazing showed modest control over algae, while nutrient addition had no general effect.
- Grazer and algal biomass were more strongly predicted by variations in grazer and eelgrass diversity than by broad environmental gradients.
- Observed large-scale patterns aligned with previous small-scale experimental findings.
Conclusions:
- Biodiversity and top-down control are critical drivers of seagrass ecosystem function.
- Biodiversity's influence is comparable to major global change stressors in these threatened habitats.