Ecology And Environment

Effect of Zebra Mussels on the Great Lakes



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If you live anywhere near the Great Lakes these days, you know all about zebra mussels. The effect of this invasive species on the Great Lakes area is far greater than you might guess from their size. These little shellfish have no natural predators in the Great Lakes ecosystem, so they just keep piling up until they clog water intakes and mess up the ecosystem. There's no getting rid of them!

How they got here

Zebra mussels are native to Russia, but they spread through all of Europe a century ago. It took them longer to get to the Great Lakes. They hitchhiked to the Great Lakes in the ballast of a transAtlantic ship sometime in the mid-1980s.

Now it's law that ships have to change fresh water ballast at sea and seawater ballast inland, so it's much harder for that kind of thing to happen again. However, that doesn't help the Great Lakes much for the zebra mussel. They're already here.

First, they were found in Lake St. Clair, between Windsor, Canada, and Detroit, in the U.S. That was in 1988. By 1992, they were in all the Great Lakes and working their way inland.

They've gotten into many of the inland lakes and rivers. They're in the Rideau River going up to Ottawa. They're as far west as Wisconsin, and as far south as the Mississippi River. They've even reached the Hudson River, so they're invading all those lakes from both the St. Lawrence River and the Hudson River.

A close relative of the zebra mussel, the quagga mussel, came to the Great Lakes right around the same time as the zebra mussel. It's just as colonial as the zebra mussel, and it's every bit as disruptive. You don't have to worry about telling them apart. Both are invasive and very destructive!

It wasn't all bad

Zebra mussels do a great job at filtering pollution out of the water. Lake Erie had a serious downturn in the 1980s, and a lot of people gave it up for dead. Some people think the zebra mussel turned that around. The perch fishery in Lake St. Clair briefly jumped to five times what it used to be!

But now that it's been turned around and Lake Erie's more or less recovered, the other effects zebra mussels bring with them are starting to become really noticeable. Those effects are causing completely new problems for the lake and the people living around it. Even the unusually clear water's causing problems.

Why they're a problem

Zebra mussels clog up pipes. They cling to each other so the colony blocks more and more of the water intake. That causes all kinds of problems for every single service and business that depends on water intake.

Water treatment plants are always hard hit. Zebra mussels make it so they're literally between a rock and a hard place! Incoming water brings in the zebra mussels, right into the main part of the plant. They start to grow all along the pipes. If they're not cleaned out regularly, it's never long before zebra mussels clog them completely.

It's really hard and expensive to open up the pipes again, and it's impossible to get rid of them completely. The zebra mussel larva is microscopic. It gets into everything.

Clogging up pipes has caused water outages, and that's bad enough. They could also become a really dangerous problem to CANDU nuclear reactors.

CANDU nuclear reactors have to be built close to large sources of water because they need regular water and heavy water for so many things. That makes them really good reactors, So much water makes them really safe reactors as well. A CANDU will shut down long before you run into a Fukushima problem. But you really don't want zebra mussels clogging up the water intake pipes!

Copper mesh

Some places are blocking intake pipes with copper-nickel mesh. It looks like it's working. Zebra mussels just don't attach to copper-nickel the way they do to just about everything else.

Of course, copper's got its own problems. For one thing, copper's poisonous to lots of marine life. That's why there aren't any zebra mussels on copper mesh. It's been known to kill everything from snails right up to fish. It can also cause long-term disruptions in fish breeding.

Water clarity

It didn't take long for that beautiful clear water to spell trouble. Zebra mussels filter out and feed on all the good phytoplankton but spit out all the toxic blue-green algae. That completely disrupts the Great Lakes ecosystems. It leads straight to toxic blooms and dead zones. Fish die!

Swimmers don't notice the problems at first. It's not like swimmers object to clear water! But all those zebra mussels hiding under the surface have a lot of sharp shells. That's a real turnoff to enjoying the waves.

Stop the spread!

If by some chance you've missed hearing about this invasive species on the news or haven't realized yet how you're affected, you'll soon see them on billboards. It's part of a zebra mussel awareness campaign which reminds boaters to drain their boats before they leave, so they won't carry the zebra mussel larva to new locations.

It's even better if you don't take your boat between different lakes until it's overwintered. Just because the zebra mussel is out of the ballast, that doesn't mean people have to HELP it spread!

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ARTICLE SOURCES AND CITATIONS
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