Classifying Lakes to Quantify Relationships Between Epilimnetic Chlorophyll a and Hypoxia
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Excess nutrient loading increases algal abundance which can cause hypoxia in many lakes and reservoirs. We used a divisive partitioning approach to analyze dissolved oxygen profile data collected across the continental United States to increase the precision of estimated relationships between chlorophyll a (chl a) concentrations and the extent of hypoxia in the water column. Chl a concentrations predicted the extent of hypoxia most accurately in lakes that were stratified at the time of sampling with a maximum temperature gradient of at least 1.2 °C/m. Lake elevation, Secchi depth, and lake geometry ratio further refined the specification of groups of lakes with different relationships between chl a and the extent of hypoxia. The statistical relationships between chl a and the extent of hypoxia that were estimated can be used directly for setting management thresholds for chl a in particular types of lakes.
KeywordsLake Hypoxia Chlorophyll a Stressor-response Classification
The authors thank B. Walsh and S. Whitlock for reviewing an earlier draft of this paper. The views expressed in this paper are those of the authors and do not reflect the policy of the US Environmental Protection Agency.
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