Inside the battle to preserve the underwater ghosts of Ontario's Great Lakes

Archeologists, historians and divers are trying to digitally capture more than 1,000 shipwrecks at the bottom of the Great Lakes before they become unrecognizable after a combination of invasive mussels and climate change have accelerated their deterioration at an alarming rate.

The Great Lakes region is known among diving circles as one of the best places in the world to explore shipwrecks because the cold, fresh water offers ideal conditions for their preservation, even in shallow water. 

Now, the deterioration of these underwater relics has not just been accelerated by more frequent and intense storms believed to be driven by climate change, but through the colonization of the lakes by invasive zebra and quagga mussels from Europe, likely introduced in the Great Lakes through ballast water of international cargo ships.

Since their arrival in the 1980s, the thumbnail-sized mollusks have transformed the Great Lakes — driving local mussels to the brink of extinction, turning once-murky turquoise waters crystal clear while at the same time blanketing almost everything — from piers to power plants — in a jagged carpet of densely packed shells. 

Durrell Martin has seen been witness to that change first hand. Over his 30-year diving career, Martin, also the president of the non-profit group Save Ontario Shipwrecks, said the invasive mussels have totally transformed the underwater world. 

When he began, lights were needed to penetrate the murky darkness of the lakes. Back then, divers had to get close to see the wrecks, but when they did, they could still see dishes, preserves and even the original wood on 200-year-old ships lying on the bottom. 

Today, the water is so clear that lights are often no longer needed, and while divers can now easily see the form of shipwrecks, they're encrusted in living layers of tens of thousands of invasive shellfish.  

"Our dilemma is that, yes, the visibility is great for scuba divers, and we now can enjoy and see wrecks more, but they are disintegrating at a faster rate than we have ever seen previously." 

Mussels affix themselves to surfaces using a bundle of threads called filaments. On wooden shipwrecks, they use these tendrils to burrow into the wood, giving them a firm hold, but weakening the wood's integrity. On steel and iron, the mussels produce an acid in their feces that corrodes metal.

The hull of a ship is designed to displace water. It is meant to withstand pressure from the bottom, not from the top. Over the years, the filaments and acid weaken the ship materials and the whole ship eventually collapses under the sheer weight of the mussels that are attached to them. 

"We can't stop this," Martin said. "Shipwrecks we thought would be here another 200 years from now and we could enjoy, we realized probably within the next 10 to 20 years, they'll all be gone. They'll be piles of lumber on the bottom."

The problem has been documented in a number of studies going back decades, but almost nothing has been done by governments on both sides of the border, according to Ken Meryman, a shipwreck hunter and diver from Duluth, Minn., who has been documenting Great Lakes naval relics for 50 years. 

"They're collapsing," he said of the 1,400 known shipwrecks in the Great Lakes.

Meryman added that the wrecks are at risk from more than just invasive bivalves — studies suggest bacteria are also being supercharged by climate change.