Classifying lakes to quantify relationships between epilimnetic chlorophyll a and hypoxia
Lester L Yuan1, Amina I Pollard
1Office of Science and Technology, Office of Water, U.S. Environmental Protection Agency, 1200 Pennsylvania Ave NW, Washington, DC, 20460, USA, yuan.lester@epa.gov.
Environmental Management
|December 5, 2014
Summary
Excess nutrients boost algal blooms, causing low oxygen (hypoxia) in lakes. Chlorophyll a levels accurately predict hypoxia extent in stratified lakes, aiding water quality management.
Area of Science:
- Environmental Science
- Limnology
- Water Quality
Background:
- Excess nutrient loading is a primary driver of increased algal abundance in freshwater ecosystems.
- Algal blooms can lead to hypoxia, a condition of low dissolved oxygen detrimental to aquatic life in lakes and reservoirs.
Purpose of the Study:
- To precisely estimate the relationship between chlorophyll a concentrations and the extent of hypoxia in lakes and reservoirs.
- To identify key environmental factors that refine these relationships for improved water quality management.
Main Methods:
- Utilized a divisive partitioning approach to analyze dissolved oxygen profile data from lakes across the continental United States.
- Examined the predictive accuracy of chlorophyll a concentrations for hypoxia extent under varying stratification conditions.
Main Results:
- Chlorophyll a concentrations were most accurate predictors of hypoxia in lakes stratified with a temperature gradient of at least 1.2 °C/m.
- Lake elevation, Secchi depth, and lake geometry ratio further improved the models by defining distinct lake groups with unique chl a-hypoxia relationships.
Conclusions:
- Statistical relationships between chlorophyll a and hypoxia extent can be directly applied for setting management thresholds.
- This approach allows for more precise water quality management strategies tailored to specific lake characteristics.
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