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Updated: Jun 13, 2026
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Understanding Dissolved Organic Matter Biogeochemistry Through In Situ Nutrient Manipulations in Stream Ecosystems
Published on: October 29, 2016
Light, nutrients, and herbivore growth in oligotrophic streams
Walter R Hill1, John G Smith, Arthur J Stewart
1Environmental Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37830-6351, USA. wrhill@illinois.edu
Ecology
|April 16, 2010
Summary
Herbivore growth in streams is linked to light and nutrients. Snail growth peaked when light was high and nutrients low, contrary to expectations, due to intense grazing pressure.
Area of Science:
- Aquatic ecology
- Ecosystem dynamics
- Nutrient cycling
Background:
- The light:nutrient hypothesis suggests herbivore growth declines with increasing light:nutrient ratios due to lower food quality.
- Aquatic ecosystems experience seasonal variations in light and nutrient availability.
Purpose of the Study:
- To test the light:nutrient hypothesis by examining seasonal effects on periphyton mineral content and snail growth.
- To investigate the relationship between light, nutrients, periphyton quality, and herbivore growth in oligotrophic streams.
Main Methods:
- Measured streambed irradiance, dissolved nutrient concentrations (nitrate, phosphate), and periphyton nitrogen and phosphorus.
- Monitored the growth rate of the snail Elimia clavaeformis in two Tennessee streams.
- Analyzed seasonal variations and their impact on light:nutrient ratios and snail growth.
Main Results:
- Light:nutrient ratios varied nearly 100-fold annually due to seasonal changes in light and inverse nutrient concentrations.
- Periphyton nutrient content was lowest when light was highest (early spring).
- Snail growth peaked in early spring, correlating linearly with primary production driven by light, not limited by low periphyton nutrients.
Conclusions:
- The study did not support the light:nutrient hypothesis's prediction of reduced herbivore growth at high light:nutrient ratios.
- Intense grazing likely reduces snail nutrient demand, making them less sensitive to periphyton mineral content.
- Competition for food resources significantly influences herbivore growth, potentially overriding nutrient limitation in heavily grazed habitats.
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