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Noah J. Langenfeld and Bruce Bugbee

Dissolved oxygen (DO) is critical for aerobic life in aquatic environments. Rapid and accurate measurements of DO are necessary to quantify the rate of oxygen uptake and maintain optimum conditions in root zones. DO meters are available across a price range of USD99 to more than USD1000. We compared three meters for stability, response time, and accuracy in freshwater [tap water, 0 g⋅L–1 sodium chloride (NaCl)] and saline water (simulated seawater, 35 g⋅L–1 NaCl) across multiple temperatures. The Yellow Springs, Inc. 550A (YSI) and Sper Scientific 850048 (Sper) meters were stable across a range of water temperatures (12–38 °C) and salinity. The Smart Sensor Roeam AR8210 drifted ±50% within minutes after calibration and was not evaluated further. In freshwater, the YSI meter was within 4% and the Sper meter was within 5% of the theoretical value at 12 and 22 °C. Meters were less accurate at 38 °C. The accuracy in saline water was similar to freshwater. Across temperature and salinity, the response time averaged 10 s for the YSI meter and 15 s for the Sper meter. We conclude that the YSI and Sper meters can provide rapid, stable, and accurate measurements of DO.