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Control of nitrogen export from watersheds by headwater streams
B J Peterson1, W M Wollheim, P J Mulholland
1Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543, USA.
Science (New York, N.Y.)
|April 9, 2001
Summary
Headwater streams significantly control nutrient export to larger water bodies. Smallest streams rapidly transform nitrogen, with implications for water quality and atmospheric nitrous oxide.
Area of Science:
- Environmental Science
- Ecology
- Hydrology
Background:
- Headwater streams are critical components of watershed nutrient cycling.
- Understanding nitrogen dynamics in these systems is essential for managing downstream water quality.
Purpose of the Study:
- To investigate nitrogen dynamics in North American headwater streams across diverse biomes.
- To quantify the role of streams in nutrient processing and export.
Main Methods:
- Utilized a comparative (15)N-tracer study design.
- Analyzed nitrogen uptake and transformation rates in various stream sizes.
Main Results:
- Smallest streams exhibited the most rapid ammonium and nitrate removal.
- Ammonium was removed within tens to hundreds of meters; nitrate traveled 5-10 times farther.
- High nitrification rates were observed, suggesting small streams as nitrous oxide sources.
Conclusions:
- Headwater streams, particularly smaller ones, play a crucial role in regulating nutrient loads to rivers, lakes, and estuaries.
- These streams significantly reduce dissolved inorganic nitrogen export during biologically active periods.
- The processing capacity of headwater streams has implications for both aquatic ecosystem health and atmospheric gas exchange.
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