Sunken Treasure

The dive flag on John Janssen’s boat flaps in the wind as the fisheries biologist watches a fellow researcher come to the surface of Lake Michigan. Wearing a snorkel mask and wetsuit, the diver—a student from the University of Wisconsin–Milwaukee—is checking the egg traps they have laid out for lake trout, a species sufferning in the Great Lakes thanks to an invasive, bloodsucking fish called the sea lamprey.

Here, under the choppy, dark surface just off the Wisconsin coast, lies a long stretch of ancient reef where lake trout spawn by the thousands. The fish often drop their eggs into the tiny crevices of rocky reefs. At 400 million years of age, the corals have long since turned to limestone. In more recent centuries, this freshwater expanse became a maritime shipping corridor and is now home to many a shipwreck. And yet, this part of Lake Michigan remains largely unmapped and unexplored—an underwater terra incognita.

“On land you can get a really nice image from a satellite,” says Janssen. “We don’t have that underwater.”

That dearth of data could soon change. Earlier this month, President Obama announced plans to create two new marine sanctuaries, one of which would encompass an 875-square-mile area of western Lake Michigan where as many as 122 ships are believed to have sunk, although the final resting places for only 39 of them are known. (The other proposed sanctuary, within Maryland’s Potomac River, is renowned for its collection of underwater wrecks as well.)

Protecting sunken ships does more than preserve a bit of history. Though restrictions differ from sanctuary to sanctuary, a designation usually keeps the site—and its marine life—safe from drilling or dredging, pillaging or destruction. These protections also encourage researchers to come discover the lake bottom’s secrets.

At Thunder Bay, the Great Lakes’ first marine sanctuary, a small team of scientists is investigating nearly 100 vessels that sank in an area of Lake Huron once known as Shipwreck Alley. But ruins aren’t all they inspect. The researchers also map the region’s topography, collect data on lake levels and temperature, and even stumble upon unexpected life-forms within sinkholes. “While we are here because of the shipwrecks, we really play an active role in protecting the Great Lakes,” says Jeff Gray, the sanctuary’s superintendent.

And for Lake Michigan, more data and maps could help scientists like Janssen take a better peek at the breeding grounds of lake trout. But there are plenty of other hidden treasures to be found—like drowned forests or remnants of Native American civilizations that once lined the lakeshore when it was 300 feet lower and 7,000 years younger.

No one knows exactly what lies beneath the waves, but one thing is certain: A new marine sanctuary will get more researchers in the water. And once they dive in, Janssen says, they’ll be in for some surprises.

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