Zebra mussels are an invasive species spreading throughout Maryland’s waterways and are moving closer to the city's reservoirs.

With the beginning of boating season at Loch Raven, Liberty and Prettyboy Reservoirs, officials are posting warning signs and handing out flyers to alert boaters to the big threat that comes in a small size.

Zebra mussels were documented in Maryland in 2008 in the Conowingo Dam and were first discovered in the U.S. in the 1980s. They've since spread as far in as Middle River and officials are worried they could end up in the city's sources for water.

“The concern is that if they're introduced into the reservoirs they will begin to settle on the intake structures and begin to line the interior of the intake piping,” said Clark Howells, the watershed section manager for Baltimore City Department of Public Works.

Zebra mussels can restrict water flow to treatment plants, impact the ecosystem by removing algae, a food source for other organisms and smother slow-moving aquatic life.

They find strength in numbers, and once the mollusks settle, they can spread quickly.

“When you have the right conditions they've been found in densities up to 750,000 per square meter,” Howells said.

Zebra mussels cannot travel on their own to the reservoirs, making them different from some other invasive species. Instead, they can be introduced into bodies of water by latching onto boats and equipment, which is why officials are asking everyone to clean off their boats, gear and bait buckets. The city also has some other safeguards already in place.

“We have a permitting system that requires all boats that use the city reservoir to have a specific permit and with that there's an affidavit saying if you use your boat in one of the city reservoirs you can use it in no other bodies of water,” Howells said.

He added that if zebra mussels were to find a way into the reservoirs, the department has means to control colonization around intake structures. But that there would be no way to completely eradicate them from the water source.

“We serve 1.8 million people in a 215 square mile surface area, so this is truly a real natural resource that needs to be preserved and protected,” Howells said.

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