Efforts to eradicate invasive quagga mussels in the Snake River are raising concerns about the potential harm to local freshwater species. A recent study published in Environmental Toxicology and Chemistry highlights the risks associated with the use of a copper-based molluscicide, which has shown to significantly decrease animal populations in the river.
Dreissenid mussels, including zebra and quagga species, are notorious for disrupting ecosystems and causing economic damage. First identified in the Great Lakes in 1988, these invasive mussels have spread across the eastern and central United States, resulting in an estimated $267 million in mitigation costs between 1989 and 2004. The recent discovery of quagga mussels in Idaho’s Snake River, near Twin Falls, marks the first occurrence of these mussels in the Columbia River Basin, prompting state officials to initiate an eradication plan.
To combat the spread of quagga mussels, Idaho deployed a 10-day treatment involving a copper-based molluscicide, comprising 28.2% copper ethanolamine and 9.1% metallic copper. Approximately 46,000 gallons of this chemical were introduced into the river. While copper treatments are commonly used in smaller bodies of water, their application in large rivers is less frequent, raising questions about ecological impact.
Researchers conducted a study to assess the effects of the copper treatment on the river’s ecosystem. They collected water samples from seven locations throughout the treatment period. The findings revealed that nearly half of the original copper mass had dissipated from the water by the end of the observation. Nevertheless, dissolved copper concentrations remained above toxic levels for more than two weeks post-treatment.
The study observed a dramatic decline in animal abundance at the sites assessed, with decreases ranging from 54% to 94%. Key species such as water nymph worms, flatworms, midge flies, and freshwater shrimp showed significant reductions in numbers, while some, including the New Zealand mud snail, the gyro snail, and the tadpole snail, disappeared entirely.
Interestingly, the treatment also led to the emergence of new organisms, including sludge worms, seed shrimp, and several insect species such as the buffalo gnat. However, the long-term implications of these changes are concerning, particularly for federally protected species that rely on the affected habitats.
The impact of copper extends almost 40 miles downstream from the treatment site, highlighting potential threats to the diets and habitats of other aquatic animals, including endangered fish species. The study underscores the need for careful consideration of ecological consequences when implementing invasive species eradication strategies.
For those interested in further details, the study titled “Fate and effects to the benthic community of a copper treatment to eradicate invasive mussels in a large western river, USA” is available in Environmental Toxicology and Chemistry and was reviewed by Andrew Zinin, an editor affiliated with Oxford University Press. The findings stress the importance of balancing invasive species control with the preservation of native biodiversity.
