Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: WEDNESDAY, August 18, 1993 TAG: 9308200061
SECTION: EXTRA PAGE: 7 EDITION: METRO
SOURCE: GREG EDWARDS STAFF WRITER
DATELINE: BLACKSBURG LENGTH: Long
The suit and a pair of hip-high wading boots stored inside the office come in handy when the Virginia Department of Transportation asks Neves to assess the impact of road projects on Virginia streams.
A research biologist with the U.S. Fish and Wildlife Service, Neves came to Tech - where he is a faculty member - in 1978 to conduct an inventory of Southwest Virginia's endangered freshwater mussels.
He is one of the world's leading authority's on mussels, also referred to as "bivalve mollusks" for their two facing shells, or "valves," which open to admit food.
The United States has the largest diversity of freshwater mussels in the world. That distinction can be attributed partly to Southwest Virginia's Clinch River, which alone is home to at least 40 different species.
When, in the early 1980s, researchers with the Tennessee Valley Authority first took Neves to the Clinch River's Pendleton Island in Scott County, he was excited to see a river bottom covered with dark slits, indicating the siphons of mussels.
The mussels, which feed by filtering river water, are important because they help to keep water clean for other river users including humans.
Mussels are the first river creatures to die off when water quality begins to decline, and their disappearance can indicate a river ecosystem is in trouble. A TVA researcher has likened mussels relationship to the river to "the canary in the coal mine."
Pendleton Island may provide such a good habitat for mussels because of the unusual stability of the rocky stream bed.
Steep bluffs protect the river's south bank and wide bottom land along the north bank allows high water to overflow in that direction. For a long distance upstream there is no significant industry to pollute the river.
The river bottom around the three small islands that collectively make up Pendleton Island is covered with round cobbles among which the mussels bury and feed. Justicia or water willow grows in abundance, adding to the stability of the mussels habitat.
Still, the mussels are in trouble.
Scientists are unsure why, but mussels in the Clinch River are not effectively reproducing. Older mussels are abundant around Pendleton Island, but young mussels are noticeably absent.
Fortunately, mussels live up to 100 years, so there is still time to try to solve the problem or save the remaining mussel species in some other way.
A female mussel can produce from 100,000 to 3 million larvae a year. The larvae live for a while as parasites on the gills of certain fish before falling to a stream bottom to begin a life of their own.
It's hard to determine what is causing the disappearance of mussels after they're gone, Neves said. Researchers are not sure if water pollution is the problem or something else.
Neves speculates that perhaps the fish hosts for the young mussels are disappearing from the river, causing their decline. Roughly 100 different species of fish live in the Clinch River, but some mussels depend on one specific fish.
Another possible explanation for the mussels decline in Southwest Virginia could be competition from Asian clams. Years ago the clams were introduced by Chinese immigrants into rivers in the Pacific Northwest as a food source. They have since spread across the United States and first showed up in Southwest Virginia in the 1970s.
The river banks near Pendleton Island are scattered with piles of small Asian clam shells, left there by muskrats, which feed on the clams as well as the native mussels.
In Virginia, the Clinch River and farther west the Powell River - also home to several endangered mussel species - are among the last undammed tributaries of the 30-million-year-old Tennessee River system, which drains five states, emptying into the Ohio River at Paducha, Ky.
As the ancestors of today's mussels moved up the river's tributaries they evolved into the diversity of species that set the river system apart today.
A more serious threat to the mussels than overharvesting is the zebra mussel, a tiny prolific shellfish from the Black and Caspian Seas that was brought to the Great Lakes not many years ago in the ballast water of a ship.
The zebra mussel has no natural predators in U.S. waters and has become a pest, reproducing in such quantities that it clogs municipal water intakes. It attaches itself to virtually every inch of native mussels and kills them by suffocation.
Having already wiped out all native mussel species in the Great Lakes, where it first appeared, the zebra mussel is now as close to the Clinch and Powell rivers in Southwest Virginia as the Tennessee Valley Authority's Fort Loudon Dam near Oak Ridge, Tenn.
If the zebra mussel finds its way into the Clinch and Powell, hitchhiking on a bass boat or by some other means, it could eliminate all the remaining native mussel species, Neves said.
Faced with failed breeding, the zebra mussel and other threats, researchers have sought ways to prevent the extinction of the remaining mussel species.
Some of their efforts include development of an artificial medium to replace fish gills as a place for mussel larvae to grow, the storage of mussels at the state fish hatchery at Marion to be used as brood stock to replace mussels in the wild and the preservation of mussel larvae by freezing them with liquid nitrogen to be brought back to life later.
by CNB