Anyone familiar with the Great Lakes has heard of Zebra Mussels. The little stripped mollusks have been on the steady incline since their introduction to the Great Lakes about two decades ago, and have caused great concern for scientists and sportsman alike. Being an invasive species that have practically no natural predators, their population has caused numerous problems with local species, sport fishing, and even lake dependent industry. Understanding the nature and reason behind these problem creatures is the beginning to their eradication.
The Zebra Mussel (Dreissena polymorpha) is a small mollusk that grows up to 2 inches wide, and lives for about 5 years. They are native to Russia, and previously to 1988 were never seen in North America. The leading theory as to how they arrived is that they were taken on in bilge water on European cargo ships, and discharged on the Canadian side of Lake St. Clair. Because a female Zebra Mussel can lie between 30,000 and a million eggs, their population exploded; and the environment has not responded well to their introduction.
The Zebra Mussel can filter up to a quart of water a day and with their numbers, have changed entire ecosystems. A good indicator of a heavy infestation (aside from visual confirmation), is observing a body go from cloudy to clear in a relatively short amount of time; though clear water may benefit some plant growth and plant eating fish, this merely serves a minor positive in an overall bad situation. In addition to starving other aquatic creatures by filtering out all the nutrients in the water, they also are known to anchor themselves onto living creatures, occasionally hindering them to immobility.
Industry and Utilities have also felt the toll from Zebra Mussels. Ships, ports, and fisheries often find themselves under siege by the never ending hoards of Zebra Mussels clinging to hulls, docks, nets, pipes, etc. Industry dependent on a constant flow of fresh water from the great lakes often find it necessary to remove masses of them from inlet pipes in order to prevent restricting the flow of water. This is particularly hazardous to nuclear power plants, which depend on the cool lake water to keep the reactors from overheating.
Current attempts to curb the Zebra Mussels ever increasing populations have overall been ineffective. Tough there a few animals that have begun feeding on them (perch, catfish, sunfish, and a few others) they still are pretty much safe from predators. Chemicals such as chlorine have been effective, but unfortunately it pretty much kills everything, including the environment that we are trying to preserve, so its use has been limited. Until a more effective means of removing them are discovered, the best we can do is brace for even more of them.