Invasive Snail Concern
Lake Michigan’s ecosystem is being threatened by a quick producing, tiny snail. The invasive creature has scientists worrying about the lake’s balance.
The New Zealand mud snail joins a rapidly growing list of nonnative species moving into the Great Lakes, threatening to disrupt the food chain and change the local environment.
The snails reproduce asexually and in large numbers, and have no natural predators in North America, said Kevin Cummings, a scientist who works for the Natural History Survey.
"It’s hard enough to contain a species once it makes its way into nonnative waters," Cummings said in a statement. "When each mud snail has the ability to produce large quantities of embryos without a partner, you’ve really got a problem."
The Illinois Natural History Survey said scientists checking Lake Michigan water samples earlier this summer found a population of the New Zealand mud snail.
The snails grow to only a few millimeters. Several dozen could sit on the surface of a dime, making them hard to spot.
Scientists say that means they could quickly spread, at high enough densities to out-compete native invertebrates for food and living space.
Rochelle Sturtevant, an ecologist with the National Oceanographic and Atmospheric Administration’s Great Lakes Environmental Research Laboratory in Ann Arbor, Michigan said scientists won’t know for some time how the mud snail will do in Lake Michigan.
The snail has been in Lake Ontario since the early 1990s and lives in high numbers there and in Lakes Superior and Erie.
"Where they’ve gotten into streams in the western part of the country, they’ve caused a lot of problems," said Sturtevant. "They’re taking over space that should have other native species living in it."
There are currently numerous invasive species that have made homes for themselves in the Great Lakes.
Zebra and quagga mussels are a threat to the region’s $4 billion-a-year fishery. They are eating up algae that is the lowest link in the lakes’ food chain.
Sturtevant said some invasive species make it possible for others to follow. The round goby, an aggressive fish native to Eurasia, now thrives in the Great Lakes because it eats zebra mussels.
Those are just a glimpse of what Sturtevant says are now at least 186 invasive species in the lakes.
Environmental groups blame oceangoing ships who introduce foreign species like mussels to the lakes.
Ships that aren’t loaded down with cargo fill their ballast tanks with water for better balance when they’re on the ocean.
Once the boats empty the tanks when they arrive in port, that ballast water often contains any number of species, from microscopic organisms to mussels and fish.
The U.S. Environmental Protection Agency introduced a plan that would require ships to dump ballast water at least 200 miles from shore. However, the permit includes an exemption for loaded ships.
Environmental groups are particularly critical of the EPA’s plan.
"I could sum it up in one word: nothing. The permit doesn’t change a thing," said Joel Brammeier, vice president for policy at the Alliance for the Great Lakes.
The shipping industry, including the U.S. Great Lakes Shipping Association, supports the idea of treating ballast tanks to kill potentially invasive species.
However, industry officials say that while treatment is being researched, so far there isn’t a feasible way to do it.
Images Courtesy USGS
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