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Long-term nutrient enrichment decouples predator and prey production
John M Davis1, Amy D Rosemond, Susan L Eggert
1Odum School of Ecology, University of Georgia, Athens, GA 30602, USA. jmdavis@isu.edu
Summary
Nutrient enrichment boosted primary consumers but not predators in a forest stream. This altered food web structure unexpectedly reduced overall food web efficiency and energy transfer to higher trophic levels.
Area of Science:
- Ecology
- Ecosystem Science
- Aquatic Ecology
Background:
- Human activities increase nutrient mobilization, posing a threat to ecosystems.
- Nutrient enrichment effects on productivity depend on food web structure and energy transfer efficiency.
Purpose of the Study:
- To investigate the impact of long-term nutrient enrichment on a forested stream ecosystem.
- To determine how nutrient enrichment affects primary consumer and predator production and food web efficiency.
Main Methods:
- Conducted a 5-year continuous nutrient enrichment experiment in a forested stream.
- Monitored primary consumer and predator production.
- Analyzed changes in the correlation between predator and prey production.
Main Results:
- Nutrient enrichment significantly increased primary consumer production.
- Predator production did not increase despite enhanced prey availability.
- The strong positive correlation between predator and prey production was decoupled, leading to nonlinear relationships.
Conclusions:
- Nutrient enrichment can truncate energy flow to higher trophic levels by altering prey community structure (favoring predator-resistant prey).
- This leads to reduced food web efficiency, contrary to predictions based on efficient trophic transfers.
- Nutrient enrichment can have unpredictable effects on ecosystem structure and productivity.
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