Are Ecotoxicologists Prepared to Tackle the Next Alien Invasion?
Tamar Schlekat, SETAC Global Science Affairs Director
A recent study published in Environmental Toxicology and Chemistry aimed to address this terrorizing issue. Austin Baldwin and his co-authors studied the impact of copper used to eradicate an invasive mussel in a large western river in the USA on the ecosystem. This is not a trivial matter; Dreissenid mussels, such as zebra and quagga mussels, are on the International Union for Conservation of Nature Global Invasive Species Database’s 100 world’s worst invasive alien species. In the U.S., they have been a nuisance in the Great Lakes since the late 80s and have spread throughout eastern and central U.S. and are now slowly making their way westward.
Zebra and quagga mussels can cause major economic and social damage. In the U.S. alone, it has been estimated that they now cost the economy more than US$1 billion annually. That cost is going to rise dramatically in the coming years as they spread in the western U.S. Those areas will be much more impacted by an invasion because they are reliant on freshwater for hydro-electric energy, agriculture, industry, fish passage and municipal uses.
Invasive mussels are typically eradicated using copper-based molluscicides and algaecides in small ponds and lakes, but their use in large rivers has been limited. However, in 2023, invasive quagga mussels were detected in the Snake River in Idaho and in the Columbia River Basin Subsequently, a 10-kilometer reach of the river was treated with about 19,300 kg (about the weight of three male African savannah elephants) of chelated copper molluscicide for 10 days. This proved to be the perfect opportunity for Baldwin and his co-authors to study the fate and effects of copper molluscicides in a large naturally flowing river and to assess the impact of such a concentration of copper on the freshwater ecosystem, including native, non-target species.
The researchers detected copper concentrations in sediment and water that would indicate the likelihood of adverse effects on aquatic species. These predictions were substantiated by measured effects in many benthic macroinvertebrates – especially the more sensitive species. Impacts of the copper treatment on fish also followed available predictions. There was nearly 100% mortality of northern pikeminnow, yellow perch, white sturgeon and largescale suckers in the treatment area where the molluscicide was applied. Common carp showed moderate sensitivity, while largemouth bass, smallmouth bass, bluegill and green sunfish were generally unaffected – likely due to their inherently lower sensitivity.
Watershed managers will increasingly face invasive species and will have to make difficult decisions in how to respond, balancing the ecological, cultural and economic risks with the protection of ecosystems and native species within. The scientists hope that “Results from this study may help inform these decisions by providing a better understanding of the downstream transport, fate, exposure and effects of a chelated copper molluscicide in a large western river.”
Full study details are online: Fate and effects to the benthic community of a copper treatment to eradicate invasive mussels in a large western river, USA.
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