Mussels in Shades Creek point to healthier water

Wednesday, April 30, 2008

Shades Creek, once thought to be ruined by decades of pollution and abuse from the Birmingham area, seems to have survived with its water quality and aquatic life intact.

Biologists say the discovery this month of a live mussel and the fresh shell of another mussel species surprised them. Mussels are sensitive to pollution and unable to move in and out as water quality changes.

So the discovery is changing how biologists view the 55-mile Shades Creek.

"It's a pearl right in Birmingham's backyard," said Bernie Kuhajda, research biologist at the University of Alabama. "It's pretty amazing."

The creek begins near the Birmingham Race Course and passes through Irondale, Mountain Brook, Birmingham, Homewood, Hoover and Bessemer before flowing into the Cahaba River in Bibb County. Until recently, it was believed that Shades Creek was so inferior that it degraded the Cahaba River where they meet.

Now, biologists are wondering if the true polluter was a bridge that until 2004 dammed the Cahaba a few miles below the confluence with Shades Creek.

Since the removal of that dam, water quality and aquatic life have improved. That success, and the discovery of the rare aquatic life in Shades Creek, lends support to those who want to remove a similar dam across Shades Creek.

This month, Kuhajda and some graduate students were surveying the creek for federally listed goldline darters. Those two- to three-inch yellow fish had been discovered in the stream a year ago.

Scientists were surprised to find them at the time, because the threatened fish had been found only in two biologically excellent stretches of rivers: the middle Cahaba below Birmingham and Georgia's Coosawattee River system.

The scientists didn't know whether the darters swam upstream from the Cahaba or their presence showed that Shades Creek was in better condition than previously believed. They returned this year and found the darters in more spots, a total of five.

At the same time, they found the mussels. One, the elephant ear, is a common species in clean streams.

They also found a fresh shell belonging to the fine-lined pocketbook, a mussel that has been critically endangered by silt and poor water quality.

"We were all pretty shocked," Kuhajda said. "This bodes well for finding other things."

Mussels reproduce only with the help of host fish, which touch the adult mussels, often seeking lures that have evolved to look like their food. The fish carry the parasitic juvenile mussels for a few weeks before dropping them.

This allows the mussels to move up and down the stream. And it makes it imperative that mussels live on passable stream channels.

About a mile above the Cahaba River, near the Bibb-Shelby county line, a bridge made of six boxcars sits across Shades Creek. A coal company is believed to have put the cars in decades ago, maybe 60 years.

The U.S. Fish and Wildlife Service has been hesitant to remove the dam, again changing the habitat and releasing the slug of silt that has built up behind the dam.

Now, the dam's removal looks more promising, said Daniel Drennen, endangered species biologist for Fish and Wildlife. He said he plans tests to ensure that the silt held back by the railcars is not toxic.

"We don't want to harm the system by trying to improve it," Drennen said.

Removing the dam would be good for canoeists, who now have to get out at the boxcars and drag their canoes past the barrier. It could also increase Shades Creek's role as a refuge for the rare and imperiled species of the middle Cahaba, said Randy Haddock, field director for the Cahaba River Society.

Haddock, who sampled Shades Creek with the University of Alabama scientists, said the discoveries benefit the entire Cahaba basin. Shades Creek is one of the river's largest tributaries.

"It's just an example of how resilient nature can be, especially in the face of severe pollution," Haddock said, "which has happened in Shades Creek, especially in the '70s, '80s and early '90s."

E-mail: kbouma@bhamnews.com

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