TOXICITY OF CHLORINE DIOXIDE TO ADULT ZEBRA MUSSELS

Chlorine dioxide (ClO2) was evaluated as a control agent for adult zeb ra mussels using single, intermittent, and continuous exposures. A sin gle 30-min exposure to 20 mg/L ClO2 or higher concentration induced at least 50 percent mortality. NaOCl, KMnO4, and H2O2 were ineffective u nder the same conditions. Intermittent chemical exposure for 30 min ea ch day indicated that ClO2 at concentrations of 10-20 mg/L can induce significant mortality over three to seven consecutive days (LC(50) = 1 3.0 mg/L), but 1-5 mg/L ClO2 applied over 28 consecutive daily exposur es are ineffective (<30 percent mortality). Identical intermittent exp osure to NaOCl was ineffective at all tested concentrations up to 30 m g/L. Continuous exposure to ClO2 for four days was effective at concen trations >0.5 mg/L (LC(50) = 0.35 mg/L), and 100 percent mortality at ClO2 concentrations >1 mg/L was achieved. NaOCl and KMnO4 were less ef fective. Pooled data yield median lethal dosages at which 50 percent m ortality occurred of 14.5 and 82.5 mg h/L for ClO2 and NaOCl, respecti vely.