AROUND 20 years ago, zebra mussels from eastern Europe arrived at the Great Lakes region of the United States via ship ballast. Since then, they have disrupted the food chain there by voraciously feeding on existing food.
The zebra mussels attach themselves to native mussels, causing the latter to be exposed to diseases and parasites. They have also colonised hard surfaces, causing damage to power and water treatment plants, boats, docks, break walls, and engines. Their ability to accumulate up to 300,000 times the amount of pollutants in their tissues causes the toxins to be passed up the food chain, which includes food normally consumed by humans. From the Great Lakes, the mussels have spread to other bodies of water in North America.
