Threat of zebra mussels keeps reservoir personnel on alert

As if the blue-green algae weren’t problem enough, Marion Reservoir officials have now added zebra mussels to their list of worries.

The unwelcomed mussels were discovered in El Dorado Lake last summer, and zebra mussel larvae recently were found in Cheney Reservoir.

Neal Whitaker, U.S. Army Corps of Engineers park ranger at Marion Reservoir, said zebra mussels are spread when water from an infected lake or river is introduced into another body of water.

The mussels have not yet been found in this area. But Marion Reservoir shares some lake traffic with both El Dorado Lake and Cheney Reservoir, so there is opportunity for the mussels to spread here, he said.

Origins and habits

The mussels originated in Western Asia and Eastern Europe and were first discovered in North America in 1988 when they were found in waters connecting the Great Lakes.

The mussels are thought to have made the transatlantic crossing in ballast water that was later discharged from ships into North American waters.

Barge traffic has continued the spread of the mussels, and the U.S. Army Corps of Engineers has issued a “Zebra Mussel Watch” for Midwestern states.

Currently, Cheney Reservoir marks the western-most edge of U.S. zebra mussel infestation.

The adult mussels look like dime-sized clams. They are frequently striped, hence the name “zebra,” but they also come in plain varieties with both light and dark colored shells.

Rapid spread

Whitaker said the zebra mussels multiply “extremely rapidly.” They are prolific reproducers capable of producing up to a million eggs a year.

After the eggs are fertilized, they develop into microscopic larvae, which cannot be seen with the naked eye. The angler or boater often unwittingly spreads them from one place to another in bilge water, live wells, bait buckets or on boats.

As the mussels mature, they attach themselves to anything firm including boats, gates, docks and buoys.

“They have been known to accumulate to the point where they would sink buoys,” Whitaker said.

Threatening water supplies

More troublesome, the zebra mussels also attach to water intake pipes.

As their populations grow, they can clog the pipes and prevent water treatment and electrical generating plants from drawing water.

“A big concern is with water intakes for the cities of Hillsboro and Marion,” Whitaker said.

Hillsboro’s plant also manufactures water for Peabody.

The zebra mussels also have a negative effect on a lake’s ecosystem.

“They are detrimental to the native mussels that are in the lake,” he said. “Both are filter feeders and the zebra mussels will out-compete the native mussels.”

He said the zebra mussels don’t attack fish, but they do harm them indirectly by competing for food.

“Being filter feeders, they take phytoplankton out of the water,” Whitaker said. “When fish are right out of the egg, the phytoplankton is their food.”

The mussels have other undesirable qualities, too.

Whitaker said their sharp shells make for unpleasant wading or swimming.

“The little devils have sharp edges and they will cut your feet,” he said.

Control techniques

Dealing with a water supply infested with zebra mussels is a challenging and costly proposition.

A variety of control techniques are being used, including filtering systems, chemical treatments and manual removal, but there is no magic bullet, Whitaker said.

“If we do get them here, there are certain mechanisms they can use to control them and those would have to be implemented,” he said.

But the best bet is to keep zebra mussels out of the lake, he said, and reservoir officials have implemented precautionary measures to do just that.

At the beginning of the summer, they began using devices provided by the Kansas Department of Wildlife and Parks to help detect the presence of zebra mussels, Whitaker said.

“It looks like a section of PVC pipe with netting inside,” he said. “It is thought to be an ideal place to find zebra mussels. So we have put those at each boat ramp.”

In addition, they recently added a test for zebra mussels to the water tests routinely performed at the lake every two weeks. This microscopic analysis will identify mussels in their larval form.

Whitaker said they have also launched an aggressive information campaign, a technique that has proven effective at controlling the spread of zebra mussels in other states.

Informational posters are hung on bulletin boards and at gatehouses and boat ramps advising boaters and anglers to take precautionary measures.

“If they are bringing boats from Cheney or El Dorado, we ask that they follow the guidelines,” Whitaker said.

Clear guidelines

The guidelines (see sidebar) provide specific instructions on draining and cleaning boats and equipment that might provide a free ride to zebra mussels.

“Even something as innocent as a minnow bucket,” he said.

Cleaning guidelines must be followed to the letter, because in certain conditions the zebra mussels can stay alive out of water for several days.

The mussels can also attach to vegetation, so lake users are advised to clean boots and other gear after leaving an infected lake.

Whitaker said he understands that following the guidelines is something of an inconvenience, but it’s the best hope for preventing or at least delaying the arrival of the mussels.

A matter of time

He’s not optimistic that they can be held off forever, though.

“It’s just a matter of time since they are so close,” he said.

And for anyone hoping that zebra mussels would eliminate the blue green algae problem at the reservoir, Whitaker said emphatically, “That is not the case.”

“The zebra mussels are selective filter feeders. While they would remove some of the beneficial algae, they will not remove the blue green algae,” he said. “They would make the situation worse.”

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