Invasive Species in Great Lakes:Zebra Mussels

by M.Foster

Great lakes facts • Great Lakes - hold 20 % of the world’s fresh water

and 95% of North America’s surface water; • The 37 million people who live in the Great Lakes

Area depend on this freshwater resource for: food, water, jobs & industry;

• The Great Lakes are one of the most invaded aquatic systems in the world, after San Francisco Bay. More than 180 different introduced species have been identified and 1-2 new species/year;

• US alone, aquatic invasives are estimated to cost more than $73 billion/year ($5 billion Zebra Mus.)

Zebra Mussels Invasion

• Zebra mussels first appeared in North America in 1988 in Lake St. Clair (btw.Lake Huron & Erie)

• Mode of introduction : via ballast water or on ancors & chains;

• Zebra mussels can survive out of water several days/weeks;

Zebra Mussels Spread• Invasives that enter the Great Lakes can then

spread across the continent through river systems such as the Mississippi to the western US;

• North America is now going through a second major expansion of these mussels, following their establishment in the Colorado River systems;

• In early 2008, larval zebra mussels were confirmed to be present in Pueblo Reservoir, Colorado, and adult zebra mussels were found in San Justo Reservoir, California;

Further Spread• Larvae spreads via water currents, fishing

activities, recreational sports;

• Adult Zebra Mussels can further spread from one body of water to another by attaching to organisms (crayfish) or boats;

• Scientists predicts that the zebra mussel will continue spreading passively, to more rivers in North America

What are Zebra Mussels?• Dreissena Polymorpha is a species of

small freshwater mussel, an aquatic bivalve mollusk, triangular in shape with an obvious ridge;

• Zebra mussels get their name from the striped pattern of their shells;

What are Zebra Mussels?• Max length - 2 inches;

• Life span of between 2-5 years;

• Preferred T - 68 and 77o F; Depths 6-24 ft;

• Prolifiration: 30,000 – 1 million eggs/year, - (most reproductive species: in 1m2 Zebra Mussel populations jumped fm 1000 to 700 000 in 6 month; Only 2 - 5% adulthood;

• By filtering 1 litre of water/day: there are now enough Zebra Mussels in Lake Erie to filter the entire volume/week;

“Life Style” & Predators• Filter-feeding organisms: remove particles

from the water, increasing water clarity and reducing pollution: particles are consumed as food, and feces are deposited;

• This biomass becomes available to bottom feeding species & to the fish;

• Zebra mussels have high nutritional value & consumed in large quantities by crayfish, waterfowl & muskrats: crayfish consumes ~105 zebra mussels/day;

Biological & Ecological Impacts

• Swimming areas become abandoned due to sharp-edged shells washing up from storms;

• Threat to Other Species: can wipe out whole populations of fish by eating all the plankton;

• May contain high concentrations of toxic materials that will harm or kill fish & wildlife;

• Interfering with their feeding, growth, movement, respiration, and reproduction;

Crayfish populated with zebra mussels

Biological & Ecological Impacts• Zebra mussels may present a health hazard

by increasing human and wildlife exposure to organic pollutants: PCB & PAH;

• Pollutants accumulated in 300,000 times greater than in the environment;

• Passing pollutants up the food chain;• Possible source of avian botulism that has

killed tens of thousands of birds in the Great Lakes since the late 1990s;

Residential, Industrial and Recreational Impacts

• Zebra mussels can harm almost every aspect of water and related resources:

• block water treatment plant intakes and pipes; restrict water flow;

• Navigation hazards: attach themselves to boats, ropes or anything else in the water;

• damage boat engine cooling systems;

• Increase corrosion of cast iron pipes;

Electrical conductor (Lake Michigan)

Eradication issues• Many chemicals kill zebra mussels, but

these exotics are so tolerant and tough that everything in the water would have to be poisoned first;

• Cost of dealing varies widely, depending on the type of facility, the length of infestation, and the control methods chosen;

• For many plants, average costs hundreds of thousands of $ per year;

Eradication issues• Controlled methods: preoxidize water at the

point of intake, chemical treatments, mechanical controls, & filtration.

• Physical barriers and chemical coatings are used to prevent zebra mussels from attaching to structures.

• Removal: with mechanical scrapers, hot water, air, chemicals, and sound; new methods are constantly under investigation.

New Research Projects• Improvement of optical techniques for mussel veligers detection• Veliger enumeration method validation• Early detection of Zebra mussels using PCR• Evaluation of filtration for excluding Zebra mussel veligers from

cooling water systems• Evaluation of ultraviolet (UV) treatment to prevent mussel

settlement in water systems• Field trials to demonstrate control of Zebra mussels using

Pseudomonas fluorescens• Coatings evaluations to prevent or minimize mussel attachment• Fish screening technologies to reduce impacts of Zebra mussels at

screened diversions• Controlling Zebra mussels with natural predators• Mussel control using copper-ion generators• Effects and spread of Zebra mussels in rivers and streams

Pseudomonas fluorescens• It is a common soil bacteria found

everywhere but harmless to humans;

• Ontario’s Ministry of the Environment has approved the one-year pilot project, which could ultimately make the product legally available to other industries: 170-megawatt power stations on Twelve Mile Creek in St. Catharines was identified as a first field trial site in Canada to test chemical-free zebra mussel killer Pseudomonas fluorescens;

Conclusion• Effective Monitoring: earliest possible detection

of new infestations for successfully planning and deploying effective control strategies

• Control solutions: proactive (excluding mussel from critical water systems) or reactive (remove from water systems after they settle)

• Ecological impacts understanding: a wealth of experience in the Great Lakes region over the last decade has demonstrated that zebra mussels infestations create significant long-term ecological changes.