Originally native to the lakes of southeastern Russia
, specifically in the Caspian Sea region of Asia, zebra mussels hitched a ride to the Great Lakes
region via ballast water from a transoceanic vessel. The ballast water was discharged into Lake St. Clair, near Detroit
, and since 1988, zebra mussels have spread to all of the Great Lakes, and have even gone as far as Tennessee
. In a period of less than four years, over 100 lakes have been affected by this invasive species. How did these mussels do it?
Many invasive species have several advantages over native species. The main factor with the zebra mussels is their reproductive rate; each female zebra mussel produces over one million eggs each year. That's a lot of zebra mussels, and that means that more of our native species in LakeOntario
are subject to this prolific havoc. They can live and feed off of many different types of aquatic environments, which puts them in a good place on the food chain. Since the mussels go through a planktonic larval stage when they are young, they can travel with the current of lakes to other shores and inlets.
The ecological impact of the zebra mussel
is tremendous. They are filter feeders, and each mussel can process up to one gallon per day. Because the density of some populations is so large, the power of the filtering abilities means that even the largest lakes can be filtered and the visibility in the water can increase. This sounds nice, having a foreign species clean our water, but there's a catch: what these animals are filtering are vital nutrients and microscopic plankton for other fish and mussels, causing some of the populations of local fish to decline over the years. And as the lakes clear, more sunlight penetrates below the photic zone, causing an increase in plant growth. More plants can be good for some species such as Northern pike and yellow perch, but for boaters, it is a nightmare because the plants can get tangled up in the motor. And for swimmers, such as myself, the feeling of algae and kelp tangling around my legs is not my cup of tea.
I remember many times when I would want to go to HamlinBeach
, but when we got there, the beach was closed because of the high plant growth and odors from eutrophication. In an indirect way, zebra mussels have affected me.
Despite all of the negative impacts on ecosystems, zebra mussels have done some good during their unwelcome establishment in our lakes. For instance, lake sturgeon, yellow perch and sunfish feed on the mussels. So far there is no effective way of eradicating the populations of these invaders, except for chemicals (which I think just adds to the problem of our polluted waters). As the old saying goes, an ounce of prevention is worth a pound of cure. So, to combat the already intense problem, boaters can check the undersides and motors of their vessels for these notorious hitchhikers. Draining live wells, and cleaning off vegetation that collects in boat hulls can significantly reduce the chance of any further spread of our zebra mussel pals.
I think the story of the zebra mussel just goes to show how much humans impact the world, just by traveling and exchanging water. The next time you go to the beach, remember that water is not just water, and the shells on the beach might be from our good friend, the zebra mussel.