Summer dissolved oxygen concentrations in forested streams of northern Louisiana

Dissolved oxygen (DO) concentrations are critical to aquatic communities and are an important measure of water quality conditions in streams. Best Management Practices that maintain shade near streams and avoid introduction of slash should minimize forest management effects on DO concentrations. However, many streams in the South Central Plains Ecoregion of Louisiana have summer DO concentrations below the 5 mg/L criterion recommended by EPA. Based on a synoptic survey of 43 least-impaired and reference forest stream reaches, we found that over 80% of these reaches had DO concentrations below 5 mg/L, and almost 60% of monitored sites had DO concentrations below 3 mg/L. These low DO concentrations are associated with low streamflow velocities and organic channel bottoms. Unachievable DO standards in the region need to be addressed to realistically reflect local environmental conditions.