The Great Lakes, a vast and vital ecosystem, face an ongoing battle against invasive species. With over 180 non-native species infiltrating these waters, roughly a third have become invasive, posing significant threats to the region's biodiversity and the well-being of its residents. This issue is not just an ecological concern but a complex web of environmental, economic, and social implications.
The Great Lakes Ecosystem
The Great Lakes, consisting of Superior, Michigan, Huron, Erie, and Ontario, form a massive freshwater system spanning between the United States and Canada. These lakes are not just bodies of water; they are lifelines supporting a diverse array of plant and animal species, including iconic fish like whitefish and lake trout, and serving as a flyway for migratory birds. Moreover, they provide drinking water for over 30 million people and sustain a thriving maritime industry, generating jobs and wages.
Invasive Species: A Growing Concern
Invasive species are non-native organisms that, once introduced, rapidly reproduce and cause harm to their new environment. They can outcompete native species for resources, act as unchecked predators, and alter habitats to their advantage. Some, like the mountain pine beetles, pose direct risks to human livelihoods by damaging crops. The ability to identify these invaders is crucial: look for species that lack natural predators in their new habitat, reproduce rapidly, outcompete natives, and cause ecosystem or health damage.
Major Aquatic Invaders
The sea lamprey, an Atlantic Ocean native, has wreaked havoc in the Great Lakes, killing up to 40 pounds of fish during its parasitic life stage. Invasive carp species, originally imported for aquaculture, have escaped and now compete with native fish for food. The round goby, a small but aggressive feeder, has spread through all five lakes, stealing food from native species. Quagga and zebra mussels, also from the Ponto-Caspian region, cause trouble by filtering zooplankton, clogging habitats with their shells, and coating water intake pipes. The rusty crayfish, native to the Ohio River basin, has spread north, eating fish eggs and destroying algal forests that smaller fish rely on.
Plant Invaders
Plant invaders have caused significant damage, too. The narrow-leaved cattail hybrid, Typha × glauca, shades out shorter wetland plants. Eurasian watermilfoil damages native plant communities and spreads quickly by hitching rides on boats. Hydrilla, originally from Asia, blocks sunlight and lowers oxygen levels in the water. The invasive subspecies of common reed chokes out other wetland plants, and its roots release chemicals suppressing nearby vegetation. Japanese stiltgrass, introduced as packing material, crowds out native ground cover and introduces diseases.
Prevention and Control Measures
Prevention efforts have focused on the primary pathway: ballast water. Ships carry water for stability, and when discharged in ports, they release any freshwater stowaways. New regulations require ships entering the Great Lakes to flush their tanks with mid-ocean saltwater, killing potential invaders. Conservation groups also work with pet and aquarium stores to identify and prevent the sale of potentially invasive species. Boaters are encouraged to rinse their equipment with hot water between waterways to kill any hitchhikers. Physical barriers on canals connecting the Great Lakes to other river systems, like the electric barriers in the Chicago Area Waterway System, help keep invasive carp out of Lake Michigan.
These measures have had a positive impact. Since the tightened ballast rules in 2006, new invasive species establishing themselves in the Great Lakes have decreased by about 85%. Removing established species is more challenging, but programs like the sea lamprey control, which uses selective lampricides, traps, and physical barriers, have shown success. Interestingly, some invasives, like round gobies, prey on young zebra mussels, providing a natural check on mussel populations.
Conclusion
While it's unlikely that the Great Lakes will ever be completely free of invasive species, the combination of ballast regulations, lamprey control, canal barriers, and targeted carp removal has made significant progress. For those living in or visiting the region, simple actions like cleaning and drying boats and gear between waterways and avoiding the use of invasive species as bait can make a difference. The fight against invasive species is an ongoing battle, but with continued efforts and awareness, the Great Lakes can continue to thrive and support the diverse life that depends on them.
