Light limitation of nutrient-poor lake ecosystems
Jan Karlsson1, Pär Byström, Jenny Ask
1Climate Impacts Research Centre, Department of Ecology and Environmental Science, Umeå University, Box 62, SE-981 07 Abisko, Sweden. Jan.Karlsson@emg.umu.se
Nature
|July 24, 2009
Summary
In many small, nutrient-poor lakes, colored organic matter from land limits light, controlling biomass production. This challenges the traditional view that nutrients are the primary driver of lake productivity.
Area of Science:
- Ecology
- Limnology
- Environmental Science
Background:
- Ecosystem productivity, the rate of biomass synthesis, is crucial for ecosystem function and management.
- Nutrient availability has been the established paradigm controlling productivity in lake ecosystems.
- Small, nutrient-poor lakes represent a majority of global lake ecosystems.
Purpose of the Study:
- To assess the relevance of the nutrient limitation paradigm for small, nutrient-poor lakes.
- To investigate the role of colored organic matter in controlling lake productivity.
- To understand how light attenuation affects biomass synthesis and higher trophic levels.
Main Methods:
- Comparison of small unproductive lakes along a water color gradient.
- Assessment of colored terrestrial organic matter's effect on light attenuation.
- Evaluation of impacts on benthic primary production, invertebrates, and fish.
Main Results:
- Colored organic matter significantly controls benthic primary production by affecting light attenuation.
- This control extends to the production and biomass of benthic invertebrates and fish.
- Findings contradict the paradigm that nutrient supply primarily dictates lake productivity.
Conclusions:
- Light limitation, driven by colored organic matter, is a key factor in many unproductive lakes, not nutrient limitation.
- Changes in terrestrial carbon cycling and organic matter export will significantly impact lake ecosystems.
- Results have implications for understanding lake ecosystem function and response to environmental change.
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