Quagga mussels are an invasive species from Eastern Europe that pose a significant environmental and economic challenge to freshwater ecosystems. These small bivalves rapidly proliferate, profoundly altering the natural balance of lakes and rivers. They outcompete native species and inflict substantial damage on aquatic environments and human infrastructure, highlighting the urgency of managing their spread.
An Invasive Threat
Quagga mussels (Dreissena bugensis) are freshwater bivalves, typically the size of a fingernail, native to the Dnieper River basin in Ukraine and the Caspian Sea. They first appeared in the North American Great Lakes in 1989, likely introduced via ballast water from transoceanic ships. This transport method allowed them to establish populations in new environments.
Once introduced, quagga mussels reproduce rapidly and colonize widely. A single female can release up to one million eggs per breeding season, developing into free-swimming larvae called veligers. These microscopic veligers disperse with water currents before settling and attaching to various surfaces using byssal threads. Their ability to colonize both hard and soft substrates, and thrive in a wide range of depths and temperatures, contributes to their success.
Altering Aquatic Ecosystems
Quagga mussels profoundly alter aquatic ecosystems through efficient filter-feeding. Each mussel can filter over a liter of water daily, removing large quantities of phytoplankton and other small particles. This intense filtration increases water clarity, which might seem beneficial but disrupts the natural food web.
Removing phytoplankton, the base of the aquatic food web, reduces food for native species like zooplankton and fish larvae, leading to population declines. Increased water clarity allows more sunlight to penetrate deeper, promoting the growth of benthic (bottom-dwelling) algae and aquatic vegetation. This shift can favor harmful algal blooms, particularly cyanobacteria, which are often unpalatable or toxic to mussels and thus left to proliferate.
Quagga mussels outcompete native species for resources and space, including native mussels, which they can suffocate. Their dense populations alter nutrient cycling, particularly phosphorus, by storing it and changing its exchange between the water column and sediments. This concentrates nutrients in the benthos, impacting the ecosystem’s energy flow and species composition.
Damaging Human Systems
Quagga mussels inflict substantial physical damage on human infrastructure. They attach to and clog water intake pipes, screens, and cooling systems of power plants, industrial facilities, and municipal water treatment plants. This biofouling significantly reduces efficiency and can lead to operational failures. For example, a single layer of mussels just 0.1 inches thick can decrease water-carrying efficiency in pipelines by 5 to 10 percent.
The mussels also impact recreational activities. They encrust boat hulls, docks, buoys, and fishing gear, requiring costly and frequent cleaning. Mussels on boat hulls can increase drag, affect steering, and clog engine cooling systems, potentially causing overheating. Their sharp shells accumulate on beaches and shorelines, posing a hazard to swimmers.
Financial Burden
Quagga mussels impose a considerable financial burden on various sectors. Monitoring, control, and mitigation efforts are expensive, involving chemical treatments, mechanical removal, and pressure washing. Industries such as hydropower, agriculture, and municipal water supply incur significant losses due to reduced operational efficiency and increased maintenance requirements. For instance, managing mussels in the Great Lakes region has been estimated to cost over $500 million annually.
The economic impact extends to tourism and recreational fishing. Ecosystem degradation and restricted access diminish their value. Water quality deterioration and disrupted fish populations reduce commercial and recreational catches, affecting livelihoods and local economies.