Toxicity of Carbon Dioxide to Freshwater Fishes: Implications for Aquatic Invasive Species Management

Carbon dioxide (CO₂ ) has been approved by the US Environmental Protection Agency as a new aquatic pesticide to control invasive Asian carps and other aquatic nuisance species in the United States. However, limited CO₂ toxicity data could make it challenging for resource managers to characterize the potential risk to nontarget species during CO₂ applications. The present study quantified the toxicity of CO₂ to 2 native riverine fishes, bluegill (Lepomis macrochirus) and fathead minnow (Pimephales promelas), using 12-h continuous flow-through CO₂ exposure at 5, 15, and 25 °C water temperatures. Resulting survival indicated that bluegill (median lethal concentration [LC50] range 91-140 mg/L CO₂ ) were more sensitive to CO₂ than fathead minnow (LC50 range 235-306 mg/L CO₂ ) across all water temperatures. Bluegill were also more sensitive to CO₂ at 5 °C (LC50 91 mg/L CO₂ , 95% CI 85-96 mg/L CO₂ ) than at 25 °C (LC50 140 mg/L CO₂ , 95% CI 135-146 mg/L CO₂ ). Fathead minnow showed an opposite response and were less sensitive at 5 °C (LC50 306 mg/L CO₂ , 95% CI 286-327 mg/L CO₂ ) relative to 25 °C (LC50 235 mg/L CO₂ , 95% CI 224-246 mg/L CO₂ ). Our results show that CO₂ toxicity can differ by species and water temperature. Data from the present study may inform decisions related to the use of CO₂ as a control tool. Environ Toxicol Chem 2020;39:2247-2255. Published 2020. This article is a U.S. government work and is in the public domain in the USA.