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On Silver Carp, Zebra Mussels, the Quagga Mussel, and the Great Lakes

Lake Michigan at Ludington, Michigan

Dan Egan of the Milwaukee Journal-Sentinel opened an article on the multiple threats to the Great Lakes ecosystems with the following:

“For thousands of years, the Great Lakes were protected by Niagara Falls on the east and a subcontinental divide on the west, but those barriers to our grandest freshwater system were obliterated over the past century so that oceanic freighters could float in and Chicago sewage could float out.

“Unwanted species have been invading with tick-tock regularity ever since.

“It is a problem that lacks the graphic horror of the Gulf oil spill, but is more environmentally catastrophic in that it unleashes a pollution that does not decay or disperse – it breeds.”

We have all learned about the Chicago Sanitary Canal, designed to deliver Chicago’s sewage to the Mississippi. I have been writing about it for a year and a half, when the U.S. Geological determined that Chicago is the greatest contributor to the Dead Zone in the Gulf of Mexico. It may also serve as a highway that would deliver Asian carp to the Great Lakes. For now there is a toll gate on the highway, the dam that replaced the sub-continental divide we cut through when we started construction of the Illinois and Michigan Canal in 1848.

String of Carp caught at Lock and Dam #26, Upper Mississippi River, Alton, Illinois

So I was familiar with the carp.

Zebra mussel attached to much larger mussel

I was also familiar with the zebra mussel, which rode into the Great Lakes in the ballast of ocean-going ships and which I wrote about early in my career as a blogger, because it is found in the Mississippi.

Quagga Mussel from the U.S. Geological Survey

I was not familiar with the quagga mussel, which also rides into the Great Lakes in the ballast of ships, but through the St. Lawrence Seaway. So do the round gobies, spiny water fleas and, most recently, the bloody red shrimp ride in in the ballast of ships. The seaway site also has a lengthy article on sustainability, which makes the claim that the Corps of Engineers makes for upgrading the locks and dams on the Upper Mississippi: barges on the Mississippi and ships through the seaway are more fuel efficient and carry more cargo than trains or trucks and don’t congest the highways.

But dams on the Upper Mississippi changed the character of the island-braided river forever and ships in the St. Lawrence Seaway are bringing in invasive species that are changing the character of the Great Lakes.

Egan’s article notes that should we drain Lake Michigan we would find the lake bed paved with the quagga mussel. In Lake Huron the chinook salmon, itself an alien species to the Great Lakes, has crashed.

A mature female quagga mussel can release as many as a million eggs a year. They are filter feeders. They rest on the bottom of the lakes with their shells open, taking in microorganisms–fish food–and water through one siphon and releasing waste through a second. They are literally filtering the life out of the Great Lakes.

Egan’s article is just one in a series he has written and the Milwaukee Journal-Sentinel has published on environmental issues facing the Great Lakes. Read a few, if only to enjoy the way he writes.


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