Unlike zebra mussels, which typically aren’t found at depths beyond 60 feet, quaggas have been plucked from waters as deep as 540 feet. The ecological damage wrought by zebra mussels is minor compared with their cousin, the quagga mussel. But today, their molluscan namesake numbers in the quadrillions in the Great Lakes alone. All that remains of the African savanna grazers are seven skeletons, including one on display at University College London. It was, they would learn two years later, the quagga mussel, named after a subspecies of actual zebras that went extinct in the 1800s. Researchers on Lake Erie found what appeared at first to be a slightly different version of the zebra mussel. Vodka-Clear Waterīut the most ominous mussel development of 1989 made no headlines. That meant the mussels now had access to a watershed that spans almost half of the continental United States. A colony was also found near the head of the Chicago Sanitary and Ship Canal that provides a man-made connection between the Great Lakes and the Mississippi River basin. Each adult mussel, which typically grows no bigger than a nickel, can filter up to a liter of water per day, sequestering inside its hard little shell all the nutrients contained within that water.īy the end of 1989, zebra mussels had turned up all across the Great Lakes, west to Duluth, Minn., south to Chicago, and east to the St. In the most heavily infested areas, they soon began to cluster atop each other like gnarled coral at densities exceeding 100,000 per square meter. The North American zebra mussel problem was made worse by the fact that they have no worthy predators in the Great Lakes. The hairs also allow a baby mussel to snag food and begin to grow a shell, which eventually weighs it down and forces the mussel to settle on a lake or river bottom. Those microscopic offspring - called veligers and as small as one-tenth of a millimeter in diameter - are covered with little hairs that help them catch currents and waves and “swim” to new locations during the first few weeks of their lives. The important thing about the zebra mussel is to not consider each one as an individual organism but instead, like a cancer cell, part of a greater scourge that metastasizes as fast as currents flow.Įach female can produce 1 million eggs per year. Scientists knew the most plausible way Santavy’s mussel could have made the trip across the Atlantic and into the Great Lakes was in the friendly confines of a freighter ballast tank. The zebra mussel had already colonized rivers and lakes across Western Europe thanks to an extensive network of canals.īiologist Sonya Santavy, who found zebra mussels in 1988. The species, native to the Caspian and Black Sea basins, was well known on that side of the Atlantic for its ability to fuse to any hard surface, growing in wickedly sharp clusters that can bloody boaters’ hands and swimmers’ feet, plug pipes, foul boat bottoms and suck the plankton - the life - out of the waters they invade. They sent it to the University of Guelph outside Toronto, where a mussel expert identified it as Dreissena polymorpha, the zebra mussel. Santavy showed a fellow scientist aboard the research boat her living “stone.” It was obvious to both of them that it was some kind of clam or mussel, but the dime-sized mollusk looked like nothing Santavy’s colleague had ever seen. And the alien organisms continued to arrive, year after year, with an almost metronomic predictability - all the way up to that steamy Wednesday morning on Lake St. Nobody gave it much thought at the time, but in the years following the Seaway’s opening in 1959, species not native to the Great Lakes, ranging from algae to mollusks to fish, started turning up at a rate never before seen. It was alive.Ī young girl sits on a mound of quagga shells at Sleeping Bear Dunes National Lakeshore in Michigan. Then she realized that one of them wasn’t a pebble at all. She tried to pull them apart but she couldn’t. But there was something odd about two of those tinier pebbles. Up came a wormless scoop of stones, the smallest of which were not much bigger than her fingertips. “I can’t even explain why it popped into my head,” Santavy tells me. She was hunting for muck-loving worms, but figured she’d take a poke into the rocks below because - well, to this day, she still doesn’t know. Clair, she whimsically dropped her sampling scoop into the cobble below. Water that could be swarming with exotic life picked up at ports across the planet.Īs Santavy and her colleagues puttered over a rocky-bottomed portion of Lake St. This often meant dumping water from the ship-steadying ballast tanks - water taken onboard outside the Great Lakes. When water levels were low or sediment high, sometimes that channel still wasn’t deep enough, forcing ships to lighten their loads to squeeze through.
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