How Invasive species are taking over a watershed, an issue for local population of plants, fish and the watershed itself!
Invasive species in the Great Lakes are a major problem for the wellbeing of aquatic life and thus also the commercial fishing industry. Areas along the Grand River watershed rely heavily on fishing, both commercial and recreational, and foreign invaders pose a threat to local ecosystems. They can disrupt food chains, nutrient recycling, and they can out-compete native species. The worrisome newcomers include rotifers, cladacera, spiny water fleas, zebra mussels, and round gobies. The major cause of entry is ballast water brought in from ships entering the St. Lawrence Seaway. They are also brought in via ballast sediments, in which invertebrate eggs are contained and then released into the fresh water.
Round goby; photo via Encyclopedia of Life.
Round gobies were introduced into Lake Erie in 1993, and by 1999 the population exploded to 350 million. While gobies are preyed upon by many native fish species, such as yellow perch, smallmouth bass, and walleye, they are also nest invaders to rock bass eggs, and prey upon yellow perch eggs. This affects commercial fishing, perch, and rock bass populations, which can ultimately overturn Lake Erie’s ecosystem.
The Eurasian spiny water flea is a predatory zooplankton that came to North America in 1982. They invaded more than 50 inland North American lakes and now affect aquatic food chains. In Lake Erie, there is high gene flow among these species, primarily because of the transportation from ships. Because of this high gene flow, the water flea has a better chance of surviving due to new variations among natural selection.
Zebra mussels; photo via USDA (Flickr).
Zebra mussels are native to eastern and northern Europe and were introduced into Lake Erie in 1988. Female mussels can lay 30,000-40,000 eggs and form larvae called veligers. Zebra mussels attach themselves to hard surfaces by use of byssal threads. Native unionid clams are now endangered due to these mussels by attaching themselves to the clams and out-competing them by feeding on diatoms and fine organic matter. Unionids will eventually die after 4-8 years of zebra mussel infestation. But unionid clams can suffocate these mussels by burrowing under soft sediments; a small comeback for these sensitive organisms.
Lake Erie photographed by WraithWorshipper.
In order to protect Lake Erie, the Grand River watershed, and the Great Lakes as a whole, regional agreements and domestic policies must be studied. The International Convention on the Control and Management of Ships Ballast Water and Sediments sets water quality standards and invasive species regulations. Also, many of these species have predators that can lower their numbers, including the Lake Erie water snake, whose diet consists mainly of round gobies. Public outreach and education is a good approach to keeping the public informed on what’s going on in their area, and respecting the wildlife regulations on hunting and fishing are all positive ways to keep Lake Erie healthy.