Zebra mussels (Dreissena polymorpha Pallas, 1771) are an invasive mollusk that cause severe ecological and economic impacts on North American water resources. More information is needed on viable operational management options to control this invader and restore water use and ecology. This study evaluates the effectiveness of a chelated copper molluscicide (Natrix®) for controlling adult zebra mussels under in situ mesocosm conditions in Lake Minnetonka, Minnesota. Zebra mussel mortality and impacts to nontarget invertebrates were assessed in response to sustained free copper exposures of 0.5 and 1.0 mg Cu/L formulated as copper ethanolamine complexes. Copper concentrations, water temperature, pH, dissolved oxygen, and specific conductance were routinely monitored throughout all mesocosms. Results demonstrated a concentration and duration-related response, with 100% mortality of zebra mussels achieved at 0.5 mg Cu/L after 72 hours of exposure and 100% mortality achieved after 48 hours of exposure at 1.0 mg Cu/L. Water quality analyses revealed that environmental conditions were compatible with zebra mussel requirements and did not impact treatment outcomes. Non-target effects on benthic invertebrates showed no differences in the low-dose treatment, though there was a decrease in the numbers of invertebrates, but not taxa richness, in the high-dose treatment. This research provides valuable information to water resource managers on a chelated copper molluscicide to better inform zebra mussel management decisions.
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