The future of the remains of shipwrecks in the Great Lakes could be in peril as part of an invasive species more than a quarter of a century ago. Between 6,000 and 10,000 shipwrecks have been recorded by experts across the Great Lakes Region, with the depths of the sinkings hindering an official number. What many of them have in common is a layer of a living creature that may ultimately destroy the sunken vessel one day.
They are called Quagga Mussels, a species of mussel that originated in Eastern Europe. Previous to the Quagga Mussel, no mussels were present in the Great Lakes. Dr. Harvey Bootsma is a professor at the School Of Freshwater Sciences at UW Milwaukee, he says that all changed in the late 1980s, when ships from Russia would travel to the Great Lakes. “If they don’t carry a full load, then they would add water to balance the ship.” That water contained the quagga muscles and their relative zebra muscles. When the mussels were released,, “they found very little competition in the Great Lakes,” and with the abundance of plankton, their main food source, “they found a habitat they could really proliferate.”
Credit to Amy Benson; U.S. Geological Survey for photo, produced by National Invasive Species Information Center, USDA
Dr. Bootsma says that the Quagga Mussel has had the greatest impact of any invasive species in the Great Lakes, and that is shown on many shipwrecks. The mussels attach themselves to any part of the sea scape, from rocks, to the sandy floors of the lakes, to shipwrecks. Dr. Bootsma says these species are causing havoc to many vessels. “If they are covering…a shipwreck, if you try to remove the mussels, (they) are attached very strongly… it’s likely you’ll pull off some of that material of the shipwreck.” Over 600 wrecks have been reported at the bottom of Lake Michigan alone, but only 200 of them are identifiable because of the depths of the water.
The population of the Quagga Mussels appears to be most prevalent in Lake Michigan, the eastern part of Lake Erie, and Lake Ontario. Dr. Bootsma says the concentration of calcium, which the mussels use to make their hard shells, is much higher in Michigan, Erie, and Ontario than in Lakes Huron and Superior.
The widespread increase in the number of mussels is causing concern among marine biologists, Dr. Bootsma adds. “Those shipwrecks, they hold a lot of history, until now they have been preserved quite well,” citing cold water temperatures in the lakes. “Now that these shipwrecks are being colonized by mussels, (they) may degrade more rapidly.” Dr. Bootsma adds that so far the famous wreck of the SS Edmond Fitzgerald appears safe in Lake Superior with the small population of these mussels. Others, such as the Appomattox, which sank into Lake Michigan just north of Milwaukee in 1905, may not be so fortunate.
Dr. Bootsma says that there is no proven way to remove a large mass of the mussels from a structure. Some municipalities are able to scrape off the mussels at water inlets if they use Lake Michigan’s water, but those are small scale operations. Dr. Bootsma adds that tarps and other toxic chemicals have been used in an attempt to kill the invasive species. But challenges within the lakes have made research difficult, including depth of the wreck and the sheer number of mussels, which Dr. Bootsma says there could be as many as 10 thousand per 1 square meter (10.8 square feet). UW Milwaukee’s School Of Freshwater Sciences has done small experiments on ecosystems, but no large mass actions have been attempted.
Dr. Bootsma says it comes down to keeping invasive species out of our lakes. “It’s a lot harder and more expensive to deal with them once they’re here than just keeping them out in the first place.”
