AWWA JAW57434

Over the past decade, the Asian freshwater bivalve mollusk Limnoperna fortunei has invaded South American waters, where its fouling has made it a major nuisance for industrial and power plants, as well as the drinking water industry. Given the rising trend in worldwide shipping traffic, a future North American invasion by the pest mussel organism is probable. Because of L. fortunei's economic threat, adequate control measures must be developed. This investigation examined L. fortunei's susceptibility to chlorine and three nonoxidizing molluscicides proven to be effective in controlling the zebra mussel Dreissena polymorpha. In general terms, two of the molluscicides were either ineffective or marginally effective at the concentrations recommended for the zebra mussel, especially at lower temperatures. The third molluscicide was the most toxic of the compounds tested; concentrations of >/=1 mg/L yielded >50% mortalities at all temperatures. At 15 and 20 degrees C, chlorine at 5 mg/L resulted in total kills after three to six weeks of exposure. At 25 degrees C, it was effective at all concentrations (1-100 mg/L), achieving 100% mortalities in 11-17 days. Temperature substantially enhanced the toxicity of all the chemicals tested, particularly chlorine. The authors concluded that the commercial formulations widely used to control the North American invading pest D. polymorpha are ineffective for L. fortunei. Furthermore, in contrast to Dreissena, which spawns over a two- to three-month period, Limnoperna has a long period of active reproduction, a fact that will further complicate its control. These findings indicate that direct extrapolation from the ample experience gained in dealing with the zebra mussel will be of limited value in meeting the challenge of L. fortunei. Includes 55 references, tables, figures.