Variation in Dissolved Oxygen Levels Between
Agricultural and Protected Streams in Loudoun
County, Virginia
Shray Vij & Ryan Nisay (PI)
Introduction
This study details the impact of agricultural runoff on levels of dissolved oxygen, primarily in hypoxic environments. Dissolved oxygen depletion is a major stressor for aquatic ecosystems, but its causes arise from several factors, often obscured by levels of pollution. We conducted a 4-week, high frequency study (224 measurements) to establish baseline DO levels and to measure the impact of a storm event. Four stream sites were sampled twice a day for a 4-week period, resulting in this quantity of measurements. The results demonstrate severe degradation in agricultural streams. On average, agricultural streams exhibited a 40% reduction in mean dissolved oxygen (5.11 mg/L) compared to protected sites (8.42 mg/L). Furthermore, 38% of all measurements from agricultural sites fell below the 5.0 mg/L state threshold for aquatic stress, a condition never observed in protected streams. This oxygen depletion wasn’t random, but rather had a small correlation with agricultural pollutants including Nitrate and Turbidity. These findings provide a tenuous association of agricultural runoff with hypoxic conditions and a lack of resilience to storm events due to the smaller dataset utilized for analysis, highlighting a need for riparian buffer restoration and nutrient management.
Declaration of competing interest
No competing interest is declared.
Acknowledgments
Author Shray Vij contributed to the interpretation of results and reviewed the final manuscript. Ryan Nisay served as PI for this study.
Funding Statement
The author would like to thank the teachers at the Academies of Loudoun and Potomac Falls High School for their valuable suggestions. This work is supported in part by funds from the Loudoun Nature Conservation Project through the ”Making Change Donation” by MainStreet Bank.
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