Halfman on Mussels – Hobart and William Smith Colleges \
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Halfman on Mussels

In an article this week in the Finger Lakes Times, Professor of Geoscience John Halfman explains how quagga mussels are pushing zebra mussels out of the Finger Lakes. Both invasive species, the quaggas are larger and do not need to attach themselves to solid surfaces to feed as do the zebras.

The article notes, “Halfman said the zebra mussels attach themselves to water intake pipes at power generating plants and water treatment plants on the lakes.”

“The utility companies had to actually hire divers to chisel these zebra mussels off their intake pipes so they would flow normally. That was obviously very expensive,” Halfman is quoted.

He explains how both species arrived attached to boats, migrating from Eastern Europe. The result has been a much clearer lake, which many see as a benefit, but the article notes this has also lead to “unprecedented weed growth that wreaks havoc on swimming, boating and fishing.”

The full article follows.


Finger Lakes Times
Quaggas Musseling In
Species taking over for zebras in Seneca Lake

David L. Shaw • April 28, 2010

GENEVA – Move over zebra, the quagga is “musseling” you out of Seneca Lake.

The tiny zebra mussel has had the Finger Lakes to itself since 1992, reproducing prolifically and attaching themselves to hard underwater surfaces in large colonies to feed on algae.

Now the bigger and more powerful quagga mussel has arrived, so far just in Seneca Lake, taking over for the zebra mussel.

Hobart and William Smith Colleges geoscience and environmental science Professor John Halfman, an expert on the Finger Lakes, said quaggas now make up 80 to 90 percent of the algae-eating mussels in Seneca Lake.

Zebras arrived in the summer of 1992, hitching a ride on ocean liners and freighters coming here from eastern European waters. They first showed up in the harbor of Detroit and spread through the Great Lakes and then the Finger Lakes.

Halfman said the zebra mussels attach themselves to water intake pipes at power generating plants and water treatment plants on the lakes.

The zebras consumed so much algae that the lake water became unusually clear, especially in the shallow areas where the zebras congregated. For the first time in years, people could see to the bottom of the lakes.

But that clarity also allowed more sunlight to reach the bottom of the lake, promoting unprecedented weed growth that wreaks havoc on swimming, boating and fishing.

“The utility companies had to actually hire divers to chisel these zebra mussels off their intake pipes so they would flow normally. That was obviously very expensive,” Halfman said.

They later figured out that they could backflush hot water through the intake pipe, killing the zebra mussel colonies. They literally boiled them to death with 100-degree water. For cottage owners, however, that was not an option.

“The Seneca Lake Pure Waters Association did a survey two years after the zebra mussels arrived of property owners on the lake and a majority of the people liked the clear water,” Halfman said. “But I’m not sure they feel that way today, given the weed growth and the alteration of the lake’s ecology and fish populations.”

Quaggas don’t need to be attached to a hard surface and do their filtering and eating of algae while free-floating or resting on the bottom of the lake. They consume so much more algae that there isn’t much left for the zebra mussels, which is why the zebras are declining in number.

Halfman said the quagga invasion is why Seneca Lake has lost much of its green look and now appears as a more blue body of water. The quaggas have cleaned the waters of the green algae, he notes.

He said the quagga came here from eastern Europe, as well, and by the same method as the zebras – attached to boats from that area that came into American waters.

So far, he said quaggas are only in Seneca Lake. But he suspects they may be in Cayuga Lake as well, since the two are connected by the Cayuga- Seneca Canal.

None have been seen in the other Finger Lakes. Both zebra and quagga mussels produce a million new mussels a year.

The clear water resulting from mussels may be good in some ways. Halfman said tourists staying on a lake or enjoying a winery overlooking a lake would rather see blue, not green, water in their vista.

He said the mussels consume a lot of the algae and plankton that lake trout eat, probably contributing to the decline in lake trout in Seneca Lake. But that also has allowed walleyes, Northern pike and large and small mouth bass numbers to increase.

The mussels can also be spread from lake to lake by seagulls, who eat them and release eggs in their feces into other lakes. He said the zebras have hard shells that can cut feet when stepped on.

“It’s not a crisis, in my mind, but it has changed the lake, for sure,” Halfman said.



About the mussels

Quagga and zebra mussels are aquatic invasive species that are native to eastern Europe. The quagga originated in the Dneiper River drainage of the Ukraine. The zebra is from the lakes of southeast Russia.

They get their name from the zebra-like striping on their shells. Both are small and typically grow to the size of a fingernail. Quagga and zebra mussels co-exist, but quagga mussels appear to out-compete the zebra for food, can colonize in deeper water than zebras and are more tolerant of cold water.