Monitoring the Behaviour of Dissolved Oxygen Levels During Stream Dry-Down in the Dry Creek Experimental Watershed
Dr. Anna Bergstrom and Dr. Kevin Roche
The Dry Creek Experimental Watershed (DCEW) is home to the native Red Band trout, a genetically pure trout species that over time has become isolated in headwater streams such as Dry Creek. For these trout, dissolved oxygen (DO) is a vital component of their survival and they, along with other organisms, require it in sufficiently high concentration. Streams in mountainous semi-arid regions often experience high temperatures in peak summer which can cause a significant decline in DO concentration. The behavior of DO in these regions, especially with regard to when hypoxic conditions occur (< 2 mg/L of DO), is still relatively less understood compared to lake and marine settings. This study aims to understand the timing and duration of hypoxic conditions through continuous monitoring of DO and water temperature at five sites in Dry Creek throughout one year. We found that DO fluctuations correlate strongly to water temperature. As water temperature increased in the summer we saw a steady decline in DO levels until the reach became intermittent. In the days leading up to dry-down we observed less predictable behavior with regards to DO, with sharp declines in DO reaching hypoxic levels across multiple days. As flows returned after the dry-down period, DO levels steadily increased as water temperature decreased. Together, our findings indicate that the Red Band trout are challenged with not only high water temperatures and stream drying, but also face the additional stress of hypoxia.
Wilken, Matthew; Bergstrom, Anna; and Roche, Kevin, "Monitoring the Behaviour of Dissolved Oxygen Levels During Stream Dry-Down in the Dry Creek Experimental Watershed" (2023). 2023 Undergraduate Research Showcase. 48.