He said the mussels appear to be creating a "distinct environment" between themselves and the ships in which sulfur-reducing bacteria flourish and cause a breakdown of iron. In all, the 120-mile-long lake is believed to hold 200 to 300 shipwrecks, many of which date to the 1700s.Ĭohn said that initial evidence from another study conducted by the museum and the University of Vermont shows that the iron spikes that hold the hulls of Revolutionary War ships together are disintegrating because of the massive colonies of zebra mussels that cover the vessels. Cohn, executive director of the Lake Champlain Maritime Museum, conducted a sonar survey of the lake in 1996 and discovered 50 historic vessels. Lawrence Seaway and the Hudson River, a team of scientists led by Arthur B. Paradoxically, it is Guyer's 10-year videotaped record of zebra mussel infestation of the Prince Willem that often is cited by underwater archaeologists and maritime historians as the most convincing evidence of the gradual ruination of shipwrecks.īut it is the zebra mussels' damage to older shipwrecks such as the Spitfire, a Revolutionary War gunboat commanded by the then-loyal Benedict Arnold in Lake Champlain, that has aroused the greatest concerns of underwater archaeologists.Įxpecting the worst from an invasion of zebra mussels into Lake Champlain through canals linking it to the St. "The ability to see under water is the reason we are diving." He conceded that zebra mussels have "blurred the detail" at his primary dive site, the wreck of the Dutch freighter Prince Willem, which has been popular with divers since 1956, when it sank in 70 feet of water off Milwaukee. "Nobody curses the zebra mussels if you are in the diving industry," Guyer said. "If this continues, divers will have to go to colder parts of the lake where there are less mussels."īut Jeff Guyer, a dive charter captain in Milwaukee who often takes 30 divers a day to Lake Michigan's most extensively dived wreck, said the "phenomenal" improvement in underwater visibility caused by the zebras is a fair trade-off for whatever damage they may cause to wrecks. "Our charter business is down because of zebras," said Russ MacNeal, owner of the Underwater Dive Center on Lake Erie, near Lorain, Ohio, and chairman of the Submerged Lands Advisory Council, which works to protect Erie's shipwrecks. The mussels colonize in such huge masses that their weight alone has been known to collapse some of the older, more fragile shipwrecks. On one hand, diving conditions have never been better because of the clear water on the other, huge masses of the pests have nearly obliterated many wrecks, and the divers' expensive wet suits are easily torn by the mussels' sharp shells. Ironically, because the mussels filter plankton and minute algae from the water and dramatically increase its clarity, shipwrecks are spotted more easily now than they were before zebra mussels accidentally were transported to the Great Lakes from Eastern Europe in the ballast of cargo ships in the 1980s.Įach tiny zebra mussel can filter a quart of water a day, and in the western basin of Lake Erie, for example, water clarity has increased by 77 percent.Īs a result, shipwreck divers often sound conflicted when they talk about the thumbnail-sized, black-and-white mussels. "They're ruining some of the most historic and best-preserved wrecks in the world." "It is so bad that we can't even see the form of some wrecks," said Brendon Baillod, a diver and director of the Milwaukee-based Great Lakes Shipwreck Research Foundation. However, underwater archaeologists only recently have begun sounding an alarm over what they say is irreversible damage being caused to historic shipwrecks by huge colonies of zebra mussels. Zebra mussels, the most aggressive of the exotic nuisance species that have invaded the Great Lakes and other inland waterways, are inflicting heavy damage on old underwater shipwrecks and jeopardizing future archaeological recovery efforts, according to maritime historians.įor years environmentalists have regarded the zebra mussel as an ecological disaster because of its potential impact on the aquatic food chain, and municipal authorities have long complained about the drinking water intake pipes that have been clogged by the pesky mollusks.
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