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Laboratory-determined Phosphorus Flux from Lake Sediments as a Measure of Internal Phosphorus Loading
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Less Agricultural Phosphorus Applied in 2019 Led to Less Dissolved Phosphorus Transported to Lake Erie
Tian Guo1,2, Laura T Johnson1, Greg A LaBarge3
1National Center for Water Quality Research, Heidelberg University, Tiffin, Ohio 44883, United States.
Environmental Science & Technology
|December 7, 2020
Summary
In 2019, reduced phosphorus (P) application led to a 29% decrease in dissolved reactive P loss from the Maumee River Watershed, mitigating harmful algal bloom severity in Lake Erie.
Area of Science:
- Environmental Science
- Water Quality Management
- Agricultural Science
Background:
- Extreme precipitation events impact global water resources.
- Heavy rainfall in 2019 led to unplanted fields in the Maumee River Watershed (MRW), affecting phosphorus (P) loads.
- March-July P loads from the MRW are critical drivers of harmful algal bloom (HAB) severity in Lake Erie.
Purpose of the Study:
- To analyze the impact of reduced phosphorus application on P loads and HAB severity in the MRW during 2019.
- To investigate the relationship between P management practices and watershed P export.
- To identify factors influencing P loss and inform HAB mitigation strategies.
Main Methods:
- Comparison of predicted vs. actual dissolved reactive P (DRP) and particulate P (PP) loads for March-July 2019.
- Correlation analysis between P loads, discharge volume, and HAB severity.
- Assessment of P application rates and their influence on watershed P loading.
Main Results:
- The 2019 DRP load was 29% lower than predicted, while PP load was similar.
- Reduced DRP loads correlated with a less severe HAB than predicted based on discharge.
- A 62% reduction in applied P corresponded to a 29% reduction in DRP loss, highlighting the impact of recent P application.
Conclusions:
- Reduced phosphorus application significantly decreases dissolved reactive P loss and mitigates harmful algal bloom severity.
- Conservation practices should prioritize P application timing and techniques to enhance watershed resilience.
- Further research is needed to quantify the impact of factors like precipitation intensity, tillage, and fallow soils on P loading.
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