We often hear about the scourge of invasive species in the United States. They have taken over the Everglades, damaged the country’s biodiversity, and make up one of the most difficult environmental problems that the USA must deal with. Even the iconic Great Lakes, the world’s largest body of fresh water and an iconic part of the border between Canada and the United States, have been affected.
Since the 1920s, the Great Lakes have been invaded by at least 162 nonnative species. Two of the more devastating ones were introduced in the past twenty years. The zebra mussel and the quagga mussel are born invaders. Both have flourished in the Great Lakes, a place where they have no natural predators and therefore no controls to stop their growth. What is the story of these two species of mussels? How did they end up in the Great Lakes? Is there any way we can stop them?
The zebra mussel originated in the Balkans, Poland, and what was the former Soviet Union. It arrived to the region in 1988 in ballast water discharged from a European ship near Detroit. When they are young, they are small and free swimming, making it easy for them to spread through the use of water currents. And spread they have; since they were introduced, they have spread to other freshwater communities in the United States and Canada.
These mussels are dangerous for two reasons. First, they displace the native mussel species, depleting the food supply of other Great Lakes aquatic species. This, in turn, damages the region’s food webs. Second, they are expensive. Along with hurting the native aquatic populations, they damage the industry. When fully grown, they clog irrigation pipes, shut down water intake pipes, foul beaches, and jam ships’ rudders. According to Living in the Environment by G. Tyler Miller and Scott E. Spoolman, these animals cost the United States and Canada a combined one billion dollars a year or $114,000 an hour.
The quagga mussel has many similarities with the zebra mussel but it is larger and more destructive. The species was first discovered in the Great Lakes in September of 1989. It was most likely introduced through the ballast water of a Russian ship. According to a study made by the University of Michigan and the Michigan State University, a mature female of one of these mussels can lay as much as 1 million eggs. This amazing reproductive rate is only one reason of why this species is so successful. It can also tolerate more extreme temperatures than the zebra mussel, something that gives it the power to spread even farther north. Just like its counterpart, it has disrupted the Great Lakes’ food web by replacing other bottom dwellers, reducing the food supply of many fish. One of the main worries about this mussel though is that it can spread through river transport. In fact, it was found in the Colorado River and its reservoir system in 2007.
There are only some things that are stopping the spread of these mussels. For example, some populations of the zebra mussels are declining thanks to a native sponge that grows on their shells, stopping them from opening their shells to breathe. There are many things you can do to help as well. New born quagga mussels are called veligers. These are larvae that are free floating, making them easy to be picked up by the bilge water of boats, letting them be transported through live wells, as well as making it easy for them to attach to boat hulls. When leaving the lake, you can the drain water from your boat and transom your well. This will prevent the mussels from leaving the lake. Also, since mussels cling to a large variety of objects, take time to clean off anything that you had in the lake, including your equipment or any vegetation you may have grabbed.
The quagga and zebra mussel species have invaded the Great Lakes. They have disrupted the ecosystems once present there and hurt our economy everyday due to the large costs that they bring. Their lack of predators and fast reproduction rates has allowed them to stay successful since they were introduced in the late 80s. All is not lost though. There are many things that you can do to prevent them from spreading to other unaffected areas. This environmental problem is one that should be in the minds of all people. It has changed the ecosystem but, if it is in the minds of the people, we may one day find a solution.