For years, biologists have warned that non-native zebra mussels threaten plant and animal species throughout the Great Lakes. Now, underwater archeologists say the mussels are also damaging historic shipwrecks. The Great Lakes Radio Consortium’s Brian Mann visited an underwater museum on Lake Champlain and has our story:
Transcript
For years, biologists have warned that non-native “zebra mussels” threaten
plant and animal species throughout the Great Lakes. Now, underwater
archeologists say the mussels are also damaging historic shipwrecks. The Great
Lakes Radio Consortium’s Brian Mann visited an underwater museum on Lake Champlain and has our story:
It’s mid-afternoon and a haze floats over the dark green water, as dive-master Doug
Jones ties his boat to a yellow buoy. New York’s Adirondack mountains rise in the distance, but our destination this morning lies below the waves. Forty feet down on the silty bottom sits the wreck of a ship known as the Burlington Bay Horse Ferry…
“I suggest you do a tour around the wreck. It is possible to duck underneath part
of the decking that’s there. Please don’t, okay. It’s very fragile, especially the spokes to the paddlewheels that are sticking out. So buoyancy control is really important.”
The horse-powered ferry is one of six ships in Lake Champlain’s Underwater
Historic Preserve. Underwater sites like this one are sprinkled throughout
the Great Lakes. From commercial barges to warships, archeologists say
these wrecks hold a vital part of the region’s history.
(Respirator check and dive master chatter)
Perched on the dive platform, I go through a final equipment check. I’m
sheathed from head to toe in a wet suit, insulation against the cold water.
(big splash)
“Now come on over here and hang onto the buoy.”
Here on the lake, each wreck has its own buoy and a network of guide ropes.
Before the ropes were installed, divers sometimes bumped against the ships’
fragile timbers. After a pause to get my bearings, I slip below the
surface.
(Air bubble ambience)
Looking down, I see the buoy chain dwindle away into shadow. As I descend,
the water is cold and thick. Forty feet down, I reach the bottom. A dozen
strokes with my flippers and there it is, a man-made shape forming itself
out of shadows and watery dust.
I glide slowly past the delicate spokes of the paddle wheel. I drift above
the intricate, exposed ribbing of the deck.
“The horse ferry is the only known example of this type of vessel in North
America.”
Chris Sabick is Director of Conservation at the Lake Champlain Maritime
Museum, where they’ve built a half-scale model of the ship and its complex
gears.
(Paddlewheel sound)
Sabick: “It was a vessel type that was fairly widespread during the
19th century. But it’s one of those vessel types that has slipped
through the cracks of history and just kind of faded away.”
The lake’s murky water preserved the horse ferry. The fresh water is cold
and calm. The silt actually protects artifacts from bacteria. In many parts of
the Great Lakes, ships like this one have rested for centuries, completely
intact.
(Shells rattling)
But now that’s changing. A box of tiny, brown and white shells has been
added to the Maritime Museum’s display. It’s a new organism – the zebra mussel.
They arrived in the Great Lakes in the late 1980s, carried in the ballast
tanks of ships. Zebra mussels have wreaked havoc on native fish and plant
species. But they’ve also coated hundreds of historic wrecks:
Sabick: “The enormous weight of hundreds of thousands of these
shells on water-logged wood can obviously cause things to collapse.”
Using wrecks like the Horse Ferry, scientists throughout the Great Lakes are
studying ways that zebra mussels actually change the water’s protective
chemistry:
Sabick: “It seems that the microenvironment that exists deep inside the mussel
layer or colony attracts a type of bacteria that accelerates the
degradation of the iron. And obviously all of these shipwrecks are fastened
with iron fasteners.”
Over time, the wrecks could literally come apart at the seams.
(water bubbles)
Back in the water, I draw close to the horse ferry’s bow. Thick layers of
shells coat the ribbing. In places, not an inch of wood is visible.
Researchers say they won’t know for several years how much damage has been
done. But as the zebra mussels continue to spread, scientists fear that
underwater museums like this one could be lost forever.
For the Great Lakes Radio Consortium, I’m Brian Mann on Lake Champlain.