Consultant's Report - Minnesota State Legislature

Potassium Salts
MINNESOTA DEPARTMENT OF NATURAL RESOURCES
Feasibility Study to Limit the Spread ofZebra Mussels from Ossawinnamakee Lake
Potassium concentrations of approximately 50 mglL are effective in preventing the settlement of
zebra mussels, but higher concentrations (between 88 and 288 mg/L) are necessary to produce
mOliality. At high concentrations, 100% mortality can be achieved in forty-eight hours.
Unfortunately, many native mussels have potassium tolerance levels that are lower than that of
zebra mussels (Sprecher and Getsinger 2000). Potassium salts are toxic to zebra mussels and
other freshwater mussel species, but they are nontoxic to fish (Waller et al. 1993).
Copper Ions
Copper ions have shown distinct toxicity toward zebra mussels. One hundred percent veliger
mortality can be achieved after twenty-four hours at 5 mg/L (Sprecher and Getsinger 2000).
Separately, Waller and coworkers (1993) reported that copper sulfate levels between 5 and 40
mg/L were effective in adult zebra mussel control, but fish and other mussel species were more
sensitive than zebra mussels at these high concentrations. There is also evidence that very low
levels of copper ions can produce zebra mussel mortality if a constant residual level is
maintained. Specifically in Ossawinnamakee Lake, cupric sulfate (as cutrine-ultra) has exhibited
positive results at low concentrations; however, this chemical also affects nontarget organisms
(Steevens et al. 2004). A further discussion of this treatment is presented at the end of Section
V.
MacroTech, Inc, has developed a device that distributes copper and aluminum to water at a low
concentration. The aluminum encourages copper ions to settle and cover surfaces, which
consequently prevents zebra mussels from settling (Sprecher and Getsinger 2000). Furthermore,
veligers are targeted by flocculation and direct toxicity. The ZM-Series devices developed by
MacroTech, Inc. could alleviate disadvantages associated with the use of aluminum and copper
alone due to the low concentrations needed when utilized together. This device would most
likely be effective in small or closed systems.
Organic Molluscicides
Some organic molluscicides are chemicals that are commercially manufactured specifically for
zebra mussel control. Many of these compounds are registered with the US EPA as effective
control agents, but they are mostly utilized in closed systems or systems that have the ability to
decontaminate the water before it encounters aquatic life (Sprecher and Getsinger 2000). These
chemicals are very effective for zebra mussel control, but they are also toxic to many fish and
other aquatic species. In addition, they can be corrosive and harmful to humans. As a result,
they are not highly recommended for use in open water systems. Regardless of the system, an
NPDES permit must be obtained prior to use due to their harmful impacts. Please refer to Table
B-1 for a list ofthese chemicals as well as lethal concentrations and exposure times.
Aside from commercially manufactured molluscicides, various organic compounds have been
targeted for zebra mussel control. Cope et al. (1997) tested forty-seven chemicals to determine
their ability to prevent the attachment of zebra mussels. Butylated hydroxyanisole (BHA), tert-
V-8
Review ofPotential Control Methods