Quagga & Zebra Mussels: What They Are & Why They're a Problem
What Are Quagga and Zebra Mussels?
Quagga mussels (Dreissena rostriformis bugensis) and zebra mussels (Dreissena polymorpha) are small, invasive freshwater mollusks that have become notorious for their rapid spread and severe impact on aquatic ecosystems and water infrastructure in North America and parts of Europe.
Native to the freshwater lakes of Eastern Europe and Western Russia, these mussels made their way to North America in the late 1980s, most likely via ballast water discharged by transoceanic ships. Once introduced, they spread quickly through interconnected waterways and overland transport by recreational watercraft.
Despite their small size—zebra mussels typically max out at 1.5 inches (4 cm) and quagga mussels at 2 inches (5 cm)—these organisms have proven disproportionately destructive. Their efficiency as filter feeders and ability to adhere to nearly any hard surface allows them to rapidly colonize and dominate new environments.
Zebra vs. Quagga Mussels: Key Differences
Though they are close relatives and share many characteristics, a few essential distinctions set these two species apart:
Zebra Mussels have a more triangular shell with dark, zigzagging stripes—hence the name. They prefer hard surfaces and are often attached to rocks, boats, and water intake structures near the shoreline.
Quagga Mussels have a more rounded, D-shaped shell and lack prominent striping. Unlike zebra mussels, they can colonize both hard and soft substrates, including deeper parts of lakes and reservoirs. This makes them even more invasive and more complex to manage.
Where Are They Found?
The initial North American invasion occurred in the Great Lakes, especially Lake Erie and Lake Michigan. From there, they spread through the Mississippi River Basin and into waterways in over 30 U.S. states and several Canadian provinces. Today, they infest significant bodies of water like Lake Mead, Lake Powell, and the Colorado River system.
In Europe, quagga and zebra mussels have moved beyond their native range and are now found in various rivers and lakes in Western Europe, raising concerns similar to those in North America.
Why Are They a Problem?
Despite their unassuming size, quagga and zebra mussels create massive ecological and economic problems. Their presence disrupts natural systems and human infrastructure in multiple ways.
1. Ecosystem Disruption
As voracious filter feeders, both species can filter up to a liter of water daily, removing plankton that native fish and other aquatic species depend on for food. This filtering makes the water unnaturally clear, allowing sunlight to penetrate deeper, promoting harmful algae growth.
The mussels also outcompete native mollusks by attaching to their shells and stealing their food, contributing to their rapid decline. Once a lake or river is infested, native biodiversity plummets.
2. Infrastructure Damage
The mussels are known to colonize water intake pipes, screens, and grates in facilities like:
Hydropower plants
Drinking water systems
Industrial facilities
Golf course irrigation systems
As they multiply, they clog these systems, reduce water flow, and corrode surfaces. This leads to decreased operational efficiency, expensive shutdowns for cleaning, and long-term infrastructure degradation.
3. Water Quality Concerns
By increasing water clarity and filtering out plankton, these mussels indirectly contribute to developing harmful algal blooms (HABs). These blooms can deplete oxygen in water, killing fish and other aquatic life. Some algae also produce toxins that make water unsafe for human consumption or recreation.
4. Economic Impact
The economic cost of managing zebra and quagga mussel infestations is staggering. Estimates suggest that the U.S. spends millions of dollars annually to control mussels and repair damaged infrastructure.
Additionally, recreational industries suffer when mussel infestations ruin beaches, foul marinas, and harm fish populations. Tourism, fishing, and property values all take a hit in infested areas.
5. Public Safety and Recreation
Beaches along infested lakes are often littered with sharp mussel shells, making them hazardous for swimmers. The shells cut bare feet and degraded the natural beauty of shorelines. Historical shipwrecks and submerged structures are also at risk, as mussels attach in thick layers and cause deterioration over time.
How Can They Be Managed?
Completely eradicating zebra and quagga mussels from a large water body is virtually impossible once they are established. However, several strategies exist for management and mitigation.
Prevention
The best solution is prevention. Public education campaigns emphasize "Clean, Drain, and Dry" practices for boaters moving between bodies of water. This includes removing vegetation, draining bilges, and drying all equipment thoroughly before launching in a new location.
Regulations on ballast water discharge and regular watercraft inspections have also helped slow the spread.
Monitoring and Early Detection
Rapid response efforts can sometimes eliminate newly discovered populations. Regular monitoring using plankton tows, underwater cameras, and environmental DNA testing helps detect infestations before they get out of control.
Chemical Treatments
Chlorine and potassium permanganate are commonly used to kill mussels in closed systems like pipes. However, these chemicals harm other aquatic life and cannot be used safely in open water.
Biological Controls
One promising biological method is Zequanox®, a natural, eco-friendly product derived from dead cells of the Pseudomonas fluorescens bacteria. When mussels ingest the compound, it disrupts their digestive systems and causes death without harming native species or corroding infrastructure.
Zequanox: A Targeted Mussel Control Solution
Zequanox represents a significant advancement in mussel management. Its key benefits include:
Selective Action: It targets only invasive mussels, sparing native aquatic life.
No Pipe Damage: Zequanox does not corrode infrastructure, unlike chlorine or copper-based chemicals.
Eco-Friendly: It's biodegradable and leaves minimal residues.
Practical: A single 6-hour treatment can kill 90–100% of adult mussels. Lower doses can target mussel larvae (veligers), preventing settlement and further spread.
Current Zequanox Status
Zequanox is approved for use in all 50 U.S. states for in-pipe treatment and in most for open water, but California and Hawaii currently limits its use to in-pipe applications. It's approved for hydropower facilities in Canada, with expanded approvals under review.
Work is underway to bring Zequanox to Europe, where the need for sustainable mussel control is growing. Collaborations with agencies like the U.S. Geological Survey are also driving new formulations for large-scale and environmentally sensitive treatments.
The Road Ahead
Quagga and zebra mussels are more than just nuisances—they're an ongoing environmental crisis. Their ability to spread quickly, reproduce prolifically, and disrupt both nature and infrastructure makes them among the most damaging aquatic invaders on the planet.
However, hope lies in targeted, sustainable solutions like Zequanox, strong prevention efforts, and public awareness. We can protect our lakes, rivers, and water systems from further degradation.
Want Help Managing a Mussel Infestation?
Invasive Species Corporation is your partner in mussel control. Contact us to learn more about using Zequanox for your facility or water body or to discuss emergency use authorizations in regions where registration is still pending.
