Historians race to find Great Lakes shipwrecks before quagga mussels

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The Great Lakes’ shipwrecks and downed aircraft are being swallowed and altered by quagga mussels, pushing maritime archaeologists and historians into a race to find and document sites before they lose any remaining physical traces, the Associated Press reported.

Wisconsin state maritime archaeologist Tamara Thomsen described the problem as all-encompassing in the lower Great Lakes, telling AP that divers encounter quagga mussels on virtually every wreck there and that the mussels can cover shipwrecks to the point that the sites become layered and obscured. The invasive mussels burrow into wooden vessels, building up in thick layers that can eventually crush parts of decks and walls, and researchers also say they produce substances that can corrode metals used in ships.

AP reported that quagga mussels have yet to establish a foothold in Lake Superior. Biologists said the lake’s water contains less calcium, a factor the researchers said quagga mussels need to make their shells. That difference has kept the wreck of the Edmund Fitzgerald—an iconic freighter lost in 1975 during a storm in Lake Superior—“safe, at least for now,” according to AP’s account of biologists’ views.

Researchers traced quagga mussels’ arrival to late 1980s, with AP reporting that the creatures were discovered in the Great Lakes in 1989 and that scientists believe they entered through ballast dumps from transoceanic freighters moving through Great Lakes ports. Over roughly 30 years, the mussels have displaced zebra mussels as the dominant invasive mollusk in the region, AP said, describing them as harderier and more tolerant of colder temperatures than their zebra-mussel cousin.

AP said quagga mussels can also change the food web dynamics of parts of the lakes by consuming suspended nutrients, which researchers described as eliminating much of the base of local food chains and, in some cases, making parts of the water clearer than before. Unlike zebra mussels, the quaggas can attach to both hard and softer surfaces at greater depths, a capability that researchers said helps them colonize the lakes’ sandy bottoms.

In the field, Wayne Lusardi, Michigan’s state maritime archaeologist, said his team is working to raise more parts of a World War II plane that crashed in Lake Huron in 1944. AP reported that divers began finding the aircraft in the 1960s and 1970s, and that Lusardi said the plane’s condition back then allowed it to appear preserved; more recently, he described the wreck as looking damaged after quagga mussels colonized it. Lusardi said, according to AP, “Divers started discovering (planes) in the 1960s and 1970s,” adding that “Some were so preserved they could fly again,” while “Now” the removed parts “look like Swiss cheese,” and he described quaggas as “literally burning holes” in the aircraft.

AP also described other wreck sites Lusardi has listed in the lower Great Lakes that have been covered by quagga mussels, including the Daniel J. Morrel, which sank during a storm on Lake Huron in 1966 and killed all but one of its 29 crew members; the Cedarville, a freighter that sank in the Straits of Mackinac in 1965 with eight crew members killed; and the Carl D. Bradley, another freighter that sank in a 1958 storm in northern Lake Michigan, with 33 sailors killed.

Historians say the invasives are also complicating efforts to locate other vessels and preserve what remains. Brendon Baillod, a Great Lakes historian based in Madison, told AP he spent five years searching for the Trinidad, a grain schooner that went down in Lake Michigan in 1881. AP reported that Baillod and fellow historian Bob Jaeck found the wreck in July off Algoma, Wisconsin, and that early photos taken by a robot vehicle showed intact rigging and dishes in the cabins, but that the site was “fully carpeted” with quagga mussels.

“It has been completely colonized,” Baillod said, according to AP. He added that the site would have been much cleaner decades earlier, and that when divers brush mussels off the wood, “it tears the wood off with it,” leaving fewer recoverable details behind.

AP reported that potential quagga mussel management options can include chemical treatments, covering mussel-covered areas with tarps to restrict water flow and oxygen, introducing predator species, or attempting to suffocate mussels by adding carbon dioxide to the water. But the article said no approach has shown promise on a large scale so far, citing Bootsma of the University of Wisconsin-Milwaukee, who told AP that the only way quagga mussels disappear from a lake as large as Lake Michigan is likely through “some disease” or “possibly an introduced predator.”

With quagga mussels still spreading in much of the region, archaeologists and historians said the work of mapping and documenting shipwrecks has become time-sensitive. AP reported that they see the loss of physical, preserved wreck remains as a loss of tangible links to the past, with Baillod saying that when wrecks disappear, the record becomes “all just a memory” and “all just stuff in books.”

AP said the story was first published Sept. 23 and updated Sept. 25 to correct the name of the Gordon Lightfoot song: “The Wreck of the Edmund Fitzgerald,” not “The Ballad of the Edmund Fitzgerald.”