Efforts to eradicate invasive mussels in Idaho’s Snake River may lead to significant declines in local animal species, according to a recent study published in the journal Environmental Toxicology and Chemistry. The research indicates that while the state aims to combat the spread of quagga mussels, the methods employed could have detrimental effects on valuable freshwater ecosystems.
Dreissenid mussels, including zebra and quagga mussels, are notorious for disrupting aquatic environments. They were first identified in the United States in the Great Lakes in 1988, likely introduced through international shipping. Since then, these invasive species have spread across the eastern and central United States, leading to substantial ecological and economic repercussions. A report estimates that from 1989 to 2004, the damage inflicted by these mussels resulted in approximately $267 million in mitigation costs for water treatment and electrical plants.
In late 2023, authorities in Idaho discovered larval and adult quagga mussels in the Snake River near Twin Falls, marking the first recorded instance in the Columbia River Basin. In response, the state implemented an eradication plan that involved treating the river with a copper-based molluscicide over a ten-day period. This treatment utilized a formulation containing 28.2% copper ethanolamine and 9.1% metallic copper, totaling around 46,000 gallons of molluscicide applied to the river.
Researchers monitored the impact of this treatment by collecting water samples from seven locations along the river during the application period. Their findings revealed concerning results: almost half of the initial copper mass dissipated from the water by the end of the observation. However, dissolved copper concentrations exceeded toxic levels for over two weeks post-treatment. Notably, the abundance of various aquatic animal species dropped dramatically, with reductions ranging from 54% to 94% at the monitored sites. This decline was primarily attributed to diminished populations of water nymph worms, flatworms, midge flies, freshwater shrimp, and pebblesnails. Furthermore, some species, including the New Zealand mud snail and the tadpole snail, vanished entirely from the river.
While some new organisms, such as sludge worms and seed shrimp, emerged following the treatment, the overall implications of the copper application raise concerns for local biodiversity. The research highlights that the impact of the treatment extended nearly 40 miles downstream, potentially affecting federally listed threatened or endangered species in the vicinity. This shift in animal diversity could disrupt the food web, posing risks to the diets and habitats of protected fish and other wildlife in the area.
The study underscores the need for careful consideration when employing chemical treatments in large river systems. As Idaho continues its fight against these invasive mussels, the balance between eradication efforts and the preservation of native species remains a critical issue.
For further insights, consult the article titled “Fate and effects to the benthic community of a copper treatment to eradicate invasive mussels in a large western river, USA,” published in Environmental Toxicology and Chemistry.
