Acute toxicity of potassium to the adult zebra mussel dreissena polymorpha
The acute toxicity of potassium (K+) to adult zebra mussels, Dreissena polymorpha, and the efficacy of using K+ to enhance the toxicity of a commercial biocide was examined. Mussels, 15-20 mm in total shell length, collected from Lake Ontario, were exposed to static concentrations of K+ for 3, 6, 12, and 24 h, and to a sublethal concentration of K+ prior to and during exposure to Clam-Trol(R) CT-2 for 6, 12, and 24 h. Tests were conducted at ambient lake temperatures of 12 degreesC and 22 degreesC and mussels were subjected to a 96 h recovery period. Valve closure was inhibited in mussels exposed to sublethal as well as lethal concentrations of K+, resulting in mussels that were nonresponsive to tactile stimulation. The median effective concentration (ED50) of K+ to induce nonresponsive mussels increased as the length of the recovery period was extended from 24 to 96 h, indicating that some nonresponsive mussels were capable of recovering 96 h after exposure to the K+ treatments. A recovery period duration of 96 h was critical in assessing mortality in mussels exposed to high K+ levels and the use of tactile stimulation to test for valve responsiveness was insufficient to identify mortality. The 24 h median lethal concentration (LC50) of K+ at 22 degreesC (400 mg/L) was found to be sixfold higher than the LC50 reported by other investigators utilizing shorter recovery periods. The LC50 of the biocide to mussels treated with K+ was not reduced, suggesting that the use of K+ to inhibit valve closure may not be useful in methods to control mussel infestations.
Wildridge
PJ
Department of Environmental and Forest Biology, State University of New York College of Environmental Science and Forestry, Syracuse, New York 13210, USA.
Werner
RG
Doherty
FG
Neuhauser
EF