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Fine Sediment Removal Influences Biogeochemical Processes in a Gravel-bottomed Stream
Joseph A Morgan1, Todd V Royer2, Jeffrey R White2
1School of Public and Environmental Affairs, Indiana University, Bloomington, 702N. Walnut Grove Ave, Bloomington, IN, 47405, USA. morgan.joseph@epa.gov.
Environmental Management
|July 31, 2019
Summary
Sediment removal in Fawn River reduced primary productivity and respiration, likely due to macrophyte removal. Nutrient retention showed minimal changes, indicating larger-scale controls on nitrogen and phosphorus cycling.
Area of Science:
- Environmental Science
- Ecology
- Biogeochemistry
Background:
- Stream ecosystems play a crucial role in watershed health through nutrient and organic matter processing.
- Streambed sediment characteristics significantly influence aquatic ecosystem functions.
- River restoration efforts, including sediment removal, aim to improve ecosystem health but can have complex biogeochemical consequences.
Purpose of the Study:
- To investigate the impact of streambed sediment removal on biogeochemical cycling in Fawn River, Indiana.
- To compare stream metabolism and nutrient (nitrogen and phosphorus) retention in restored versus unrestored river reaches.
- To identify mechanisms driving observed differences in biogeochemical functions at the reach scale.
Main Methods:
- Measured stream metabolism (primary productivity and ecosystem respiration) in restored and unrestored river sections.
- Assessed nitrogen (N) and phosphorus (P) retention in both reaches.
- Analyzed properties of streambed sediments from restored and unrestored areas.
- Quantified denitrification enzyme activity in sediments.
Main Results:
- Sediment removal resulted in lower primary productivity and ecosystem respiration in the restored reach, attributed to macrophyte removal and altered sediment organic matter.
- Nitrogen and phosphorus retention showed minimal differences between restored and unrestored reaches.
- Denitrification enzyme activity was reduced in sediments from the restored reach, suggesting decreased nitrogen removal capacity.
- Near-term changes in biogeochemical function were primarily linked to macrophyte removal.
Conclusions:
- Streambed sediment removal can alter stream metabolism and nutrient cycling, with initial impacts driven by associated macrophyte removal.
- Nitrogen and phosphorus retention appear to be regulated by factors operating at larger spatial or temporal scales than the reach studied.
- Further investigation is needed to understand the long-term effects of sediment removal on riverine biogeochemical functions.
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