While most of the Chesapeake Bay may be safe from the fast-breeding zebra mussels that are creating havoc in the Great Lakes, Baltimore's watershed officials will spend $6 million to defend inland streams and reservoirs from the invaders.
The fingernail-sized bivalves from Eastern Europe have clogged waterworks and attached themselves to boats and piers wherever they have appeared, disrupting water supplies and causing millions of dollars in damage.
"I believe we will be seeing zebra mussels in fresh waters in Maryland . . . in this decade," said Dr. Vic Kennedy of the University of Maryland Center for Environmental and Estuarine Studies.
Dr. Kennedy spoke before 100 scientists, public officials and industrial representatives gathered in Baltimore last week for a two-day Mid-Atlantic Zebra Mussel Conference.
When it arrives, he said, the black-and-white striped mollusk can be expected to colonize any unprotected hard surface, including boat hulls, engines, piers, water intakes, cooling and firefighting systems. It may displace native freshwater mussels, some of which already are endangered.
In the Great Lakes, zebra mussels have covered rocks, piers and sunken cars to depths of five inches. Where conditions are ideal, they can accumulate to depths of two feet or more in a season, at a density as high as 700,000 mussels per square yard.
Anti-fouling paint, silicone-based coatings, chlorine, biocides and regular scraping can be effective against zebra mussels. But these measures also can be a nuisance, environmentally risky, expensive, or all three.
Zebra mussels aren't all bad. Diving ducks and some fish species eat them. The mussels also are voracious filter feeders, and may actually clear up some murky stretches of Maryland's waters, scientists say.
While that has helped some light-dependent plants and animals in the Great Lakes, the new competition for the microscopic algae and other organisms that cloud the water has also depleted other species, creating unpredictable imbalances in local ecosystems.
In the Chesapeake Bay, salt levels probably will be too high for the zebra mussel to survive and reproduce south of Harford County and below Quantico on the Potomac.
For that reason, Dr. Kennedy said, "I don't really believe the zebra mussel is going to be much of a problem for oysters in the Chesapeake." Ditto for blue crabs.
He was less certain about a related invader called the "quagga" mussel. It has been found among zebra mussels in the Great Lakes, but little is known of its ability to thrive in salty water.
The conference was organized by the Mid-Atlantic Sea Grant Network, a consortium of universities and public and private interests in New Jersey, Delaware, Maryland, Virginia and North Carolina.
Although no zebra mussels have yet been identified in any of those five states, the participants gathered here to learn more about the Great Lakes experience, and to get a step ahead of the invasion before it arrives.
zTC "If you want to escape going through what we did, don't wait until this animal gets established in your shop," warned Will LePage, a waterworks official from Monroe, Mich.
Clogging up the works
His town of 24,500 found itself without drinking water for 56 hours in December 1989 when a combination of fast-growing zebra mussels and ice completely clogged the intake line from Lake Erie. It took a nightmarish 18 months and more than $787,000 to clean the line and keep new invaders at bay.
Zebra mussels were inadvertently released into the Great Lakes in 1986 or 1987 by a ship discharging ballast water obtained somewhere in Europe. They have since carpeted some sections of the Great Lakes, especially Lake Erie. They also have hitchhiked aboard barges plying the Inland Waterway System to the Erie Canal and Hudson River, the Ohio, Mississippi and Tennessee rivers, and tributaries as far off as Oklahoma.
While there are no zebra mussels yet in Maryland, they have been found in West Virginia tributaries to the Ohio, and in the Susquehanna River below Binghamton, N.Y. Natural resources officials believe the bivalves will eventually get here, either by floating down the Susquehanna, or being carried from infested areas aboard recreational boats, trailers or in bait boxes.
Maryland monitors sites
Monitoring stations are looking for the first arrivals at 24 sites in Maryland. Baltimore City has already launched efforts to secure its water system.
Fearing anglers might bring zebra mussels into the reservoirs, the city last year closed its Liberty and Prettyboy reservoirs to boating. The Loch Raven reservoir was closed to all but its own rental boats.
This year, the reservoirs are being reopened to private boats, provided anglers sign a pledge to use the boats only on the three reservoirs. Gasoline engines, which can hide mussels in their cooling intakes, and boats longer than 18 feet are still banned. So is live aquatic bait.
But these are just holding actions. Gene Scarpulla, assistant watershed manager for the Baltimore City Department of Public Works, said zebra mussels "are on their way."
To protect water intakes at the three reservoirs and on the Susquehanna River, as well as 67 miles of water tunnels connecting them with Baltimore's filtration plants, the city is preparing to spend $6 million. The money will buy chlorine treatment systems to kill mussels entering the system at the Susquehanna River, and Liberty and Loch Raven reservoirs.
At Prettyboy Dam, a heat-treating system will be installed to kill mussels in the water release gear. Chlorine can't be used there because water released from the dam flows into the Gunpowder Falls, which is a prime trout stream. To prevent heat pollution of the stream, the heated water will be cooled again before release.