Waging War Against the Zebra Mussel 409 changes, extreme temperature changes are required to kill the mussels These extreme temperature changes will also kill a number of native species residing in the lake. There are two thermal treatment strate gies that can be employed: acute thermal treatment and chronic thermal treatment [Boelman 1997. Acute thermal treatment involves rapidly increasing the water temperature to lethal levels followed by a rapid return to original temperature levels. This method is most appropriate for treating infestation in waterways where a higher temperature cannot be maintained for an extensive period of time. greatly increasing the water temperature for a period of 3-9 hours can yield 100% mortality Chronic treatment involves continuously maintaining a higherwater temperature and is a cost-effective strategy for industries that generate and discharge heated water. This method prevents new zebra mussel infestations. This strategy is lethal to most if not all organisms that use the water. The water temperature, in this method, must be raised to greater than or equal to 34 C and must be maintained for 6-24 hours to kill the entire zebra mussel population Chemical treatments. Chemical treatments are an alternative to thermal treat ment but are more environmentally invasive. Both oxidizing and nonox idizing chemical treatments are available. Oxidizing treatments are most toxic to zebra mussels when applied rapidly due to the mussels sensi tivity to oxidizing compounds, whereas nonoxidizing chemicals can be administered over a longer period of time with equal effectiveness Of the oxidation treatments available, chlorination is the most widely used method for eradicating zebra mussels. There are large environmen- tal consequences to this method, and terrestrial organisms and birds may also be killed c. Potassium permanganate is another commonly used oxidizing chemi cal. To obtain 100%zebra mussel mortality, a higher concentration of and a longer exposure to potassium permanganate is required than for chlo rinated compounds. The advantage to using potassium compounds is that they are nontoxic to higher organisms like fish but are highly toxic to zebra mussels. Also, potassium permanganate by-products do not form carcinogenic compounds as is the case when using chlorinated reagents Nonoxidizing molluscicides, such as Mexel 432, are the best available chemical treatments, albeit more expensive than oxidation treatments The greatest advantage to this strategy is that molluscicides have fewer direct consequences on native organisms and fewer long-term environ- mental impacts since many of these molluscicides rapidly biodegrad into harmless substances. These reagents induce their effect in three ways On clean surfaces, the film prevents settlement. On infested surfaces, the molluscicides attack the zebra mussel byssal threads, causing the mussels to detachWaging War Against the Zebra Mussel 409 changes, extreme temperature changes are required to kill the mussels. These extreme temperature changes will also kill a number of native species residing in the lake. There are two thermal treatment strate￾gies that can be employed: acute thermal treatment and chronic thermal treatment [Boelman 1997]. Acute thermal treatment involves rapidly increasing the water temperature to lethal levels followed by a rapid return to original temperature levels. This method is most appropriate for treating infestation in waterways where a higher temperature cannot be maintained for an extensive period of time. Greatly increasing the water temperature for a period of 3–9 hours can yield 100% mortality. Chronic treatment involves continuously maintaining a higher water temperature and is a cost-effective strategy for industries that generate and discharge heated water. This method prevents new zebra mussel infestations. This strategy is lethal to most if not all organisms that use the water. The water temperature, in this method, must be raised to greater than or equal to 34◦C and must be maintained for 6–24 hours to kill the entire zebra mussel population. Chemical treatments. Chemical treatments are an alternative to thermal treat￾ment but are more environmentally invasive. Both oxidizing and nonox￾idizing chemical treatments are available. Oxidizing treatments are most toxic to zebra mussels when applied rapidly due to the mussel’s sensi￾tivity to oxidizing compounds, whereas nonoxidizing chemicals can be administered over a longer period of time with equal effectiveness. Of the oxidation treatments available, chlorination is the most widely used method for eradicating zebra mussels. There are large environmen￾tal consequences to this method, and terrestrial organisms and birds may also be killed. Potassium permanganate is another commonly used oxidizing chemi￾cal. To obtain 100% zebra mussel mortality, a higher concentration of and a longer exposure to potassium permanganate is required than for chlo￾rinated compounds. The advantage to using potassium compounds is that they are nontoxic to higher organisms like fish but are highly toxic to zebra mussels. Also, potassium permanganate by-products do not form carcinogenic compounds as is the case when using chlorinated reagents. Nonoxidizing molluscicides, such as Mexel 432, are the best available chemical treatments, albeit more expensive than oxidation treatments. The greatest advantage to this strategy is that molluscicides have fewer direct consequences on native organisms and fewer long-term environ￾mental impacts since many of these molluscicides rapidly biodegrade into harmless substances. These reagents induce their effect in three ways: • On clean surfaces, the film prevents settlement. • On infested surfaces, the molluscicides attack the zebra mussel byssal threads, causing the mussels to detach