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Drought Puts Mussels at Risk: As Streams Dry Up, Some Species Might Go Extinct in the Wild

Posted on: Wednesday, 2 January 2008, 06:00 CST

Some imperiled species of freshwater mussels in North Carolina could disappear from the wild as the drought drains the creeks where they cling to life, scientists say.

The Tar spinymussel, found only in Eastern North Carolina, primarily in the Tar River basin, has been on the verge of extinction, surviving only in a handful of streams. The Carolina heelsplitter, another endangered species in North and South Carolina, lives only slightly farther from the edge of oblivion.

Now the dry spell could tip the balance.

"A lot of streams that support imperiled mussels were dry for a prolonged period during the summer and are still very low," said John Fridell, endangered species biologist for the U.S. Fish & Wildlife Service. "We could potentially see the extinction of both these species in the wild if these drought conditions continue."

Of 10 streams that support populations of Carolina heelsplitters, Fridell said, only two had flowing water in October, when biologists last did monitoring. They noted a number of dead mussels.

North Carolina is home to more than 60 species of freshwater mussels. More than half of those are designated as endangered, threatened or of special concern because of dwindling populations.

Though freshwater mussels lack the appeal of some endangered species, they play an important role in nature. They spend most of their lives at the bottom of creeks, filtering water for food and oxygen. They keep streams and creeks clean by digesting algae, bacteria and decaying organic matter. And they provide food for raccoons, muskrats and other animals.

Their decline is a telltale sign that a river or stream has become overloaded with sediment or polluted by too much fertilizer or sewage.

"The freshwater clams don't have the sex appeal or charisma that a panda does," said Art Bogan, curator of aquatic invertebrates at the N.C. Museum of Natural Sciences. "But if we lose the Tar spinymussel, it's the same as losing the panda. It's a unique species. Once it's gone, you can't replace it. Nothing can step in its place and fill its niche."

Researchers spent two weeks last summer in the Tar River watershed searching for the spinymussel, which grows to about 2 1/2 inches long. They found fewer than a half-dozen and only in Little Fishing Creek, a tributary of the Tar River.

"We aren't sure how many are out there," said Chris Eads, an aquatic biologist who works under the direction of Jay Levine at N.C. State University's College of Veterinary Medicine. "We know there are very few."

At Levine's lab, known as the "mussel barn," Eads and others are trying to stave off extinction of these species.

The lab contains a maze of plastic piping, gurgling aquariums and tubs of water filled with mussels. Some mussels are the size of a quarter or a half-dollar; others are juveniles no bigger than a speck of sand.

The researchers, funded by federal grants to protect endangered species, are propagating Carolina heelsplitters and about a half-dozen other mussel species in hopes of rebuilding their populations in the wild.

"We're pretty much focused on one main goal: trying to prevent the extinction of species that are markedly imperiled in North America," Levine said. "There is a strong likelihood we will lose one or more of these species. We actually have more animals in captivity that we have propagated than are in the wild now."

Next year, Levine and his assistants will try to raise Tar spinymussels in partnership with the state Wildlife Resources Commission -- if they are lucky enough to collect a female with fertilized eggs.

This year, researchers placed about 40 lab-raised wavyrayed lampmussels, another imperiled species, in the Cheoah River in Western North Carolina. It was the first experimental colony in a much bigger project to re-establish the native mussel in a stretch of the river where flowing water has been restored after changes to a hydro-dam.

Eads, the aquatic biologist, said the researchers raised roughly 15,000 juvenile wavyrayed lampmussels that they will attempt to grow and reintroduce in the next few years.

"The streams they are found in now are degrading rapidly because of the suburban sprawl in that area," Eads said. "The streams are coming apart at the seams. We're looking at other places to re-establish populations that hopefully would be safer from development."

wade.rawlins@newsobserver.com or (919) 829-4528

Source: The News & Observer

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