Newly created riparian ponds during stream restoration: diel oxygen fluctuations

Authors: D. Riley Rackliffe, Douglas Fairbanks, Russell R. Rader

Year: 2012 (xliv)

Abstract

Riparian wetlands have only recently been included in stream restoration efforts even though they increase overall biodiversity and may play a critical role in determining rates of ecosystem function. In Hobble Creek, a tributary to Utah Lake, riparian ponds may also create potential rearing habitat for the endangered June sucker (Chasmistes liorus). However, summer-time fish kills have been observed in some ponds presumably attributed to low dissolved oxygen levels. We collected data on dissolved oxygen, vegetation percent cover, and pond physical characteristics. Our data suggests that water depth (< 30 cm deep), shading, and the abundance of algae may determine the duration of nighttime low oxygen levels in the summer. Atmospheric oxygen enters aquatic systems across the air-water interface, or as a byproduct of photosynthesis. In shallow ponds dissolved oxygen concentrations are largely determined by rates of photosynthesis versus rates of respiration. Algae rich shallow ponds (periphyton, filamentous greens, Chara) reached levels as high as 500% DO by day and as low as 20% at night. Algae allow oxygen produced during photosynthesis to ‘leak’ from the cell wall causing dissolved oxygen levels to increase during daylight hours whereas, rooted macrophytes do not ‘leak’ oxygen to the surrounding water but may decrease rates of photosynthesis because of shading. At night when photosynthesis has halted cellular respiration and decomposition consume oxygen. However, deeper ponds may be more resistant to the nightly lows increasing the likelihood of fish survival. These observations will be used to design an experiment showing the effects of algal abundance, shading and water depth on oxygen concentrations in shallow waters.