Wewahitchka, Fla. — The debate: Who has the biggest need for 1 billion gallons released daily from Lanier to keep the river — and the mussels — alive?

Several hundred miles of river downstream from Atlanta, a federal fish biologist wedges a motorized johnboat onto a small jut of land and jumps out to inspect a mud patch the size of a baseball diamond.

Her river sandals disappear into the muck, then slowly pop out with a slight sucking sound. At the edge of a small pool of water, she bends down to pull up a palm-sized mussel. Arching around its heavy black shell are three prominent ridges that give the freshwater mollusk its name: the fat threeridge.

Its shell is half-open, showing off a translucent white interior once prized for buttons and jewelry. Its meaty innards are shriveled down to the nub.

Everywhere she looks on the bank of the Apalachicola River are other fat threeridge mussels, half-open and dead, some partially buried in mud and poking up like headstones. They are the last of their kind, an endangered species found only in this part of the world.

"We could spend a couple of hours out here and count over 1,000," says Karen Herrington, as she surveys the dead mussels. She's with the U.S. Fish and Wildlife Service in Panama City and has been studying Apalachicola's mussels for four years.

The fat threeridge, and its larger cousin, the purple bankclimber, have become flash points in an epic debate over how best to manage dwindling water supplies during the worst drought ever seen in the Southeast.

Arguments are often reduced to man against mussel, and there's some truth to that simple equation. The U.S. Army Corps of Engineers releases billions of gallons of water daily downstream to Florida from Lake Lanier, metro Atlanta's main water source, in part to protect the threatened and endangered mussels that die without water. But like most environmental issues, the reality is much more complicated.

The public outrage, led by Gov. Sonny Perdue, has raised interest in an aquatic animal few biologists even want to study. The list of what's not known about the freshwater mollusks is a long one, starting with how many still live in the 107-mile river stretching through the Florida Panhandle. Biologists also don't know how long the mussels can survive without water, how fast they move and which fish host their eggs.

The biggest unknown is how much — or really, how little — water the mussels need to survive in the Apalachicola River, which gets its water from Lanier via the Chattahoochee River and the Flint River.

The question has never before been asked, at least not officially, even though the answer could mean the difference between draining Lake Lanier and getting through this drought without drying up most of metro Atlanta.

Minimum not for mussel

For all the brouhaha over the mussels, they only recently became part of the debate over how much of Lanier's water the U.S. Army Corps of Engineers should send to Florida's Apalachicola River, especially in a drought.

Last year, the U.S. Fish and Wildlife Service identified stretches of the Apalachicola as critical habitat for the threatened and endangered mussels, and concluded the species would survive with at least 3.2 billion gallons of water flowing daily into the river. To maintain that flow to Florida, the corps has to release more than 1 billion gallons a day from Lanier, several hundred miles upstream.

But the corps set Apalachicola's minimum flow many years ago, for reasons other than the mollusks. Records dating back to 1929 show the powerful Apalachicola has never fallen below a minimum flow of 3.2 billion gallons of water, even during droughts. And the corps wants to make sure a small coal-fired power plant on the Apalachicola that serves 19,000 homes has enough water to continue operating.

Normally, the Apalachicola River has plenty of water this time of year. The meandering waterway frequently spills into its flanking sloughs and swamps and flushes life-giving fresh water into Apalachicola Bay for its world-renowned oyster industry and popular sport fishery.

Only four rivers in the continental United States send more water to the sea than the Apalachicola: the Mississippi, Columbia, Mobile and Susquehanna rivers. Of all the rivers in the world, the Apalachicola is ranked 82nd largest based on how much water it sends to the sea each year.

As federal fish and wildlife biologist Jerry Ziewitz says, "It is not a creek."

In fact, when Gulf Power's Plant Scholz opened on the Apalachicola in 1953, just two miles downstream from where the Chattahoochee and Flint rivers meet at the state line, the concern was too much water, not too little. The plant predated the big federal dams on the Chattahoochee, including Lanier.

A 570-foot canal built between the Apalachicola and the plant's intake structure can pull in about 130 million gallons of river water a day for cooling steam. During the 1994 flood that also swamped much of southwest Georgia, the river's waters rushed up the canal and flooded the plant.

On a maintenance road at Plant Scholz, operations manager Kenny Peacock, who saw it happen, points to a mark on the ground just behind the intake structure that shows how far the waters reached that year. Behind him, on much higher ground and at least 100 yards away, is the plant itself, a hulking structure with its original brick smokestack.

But in protecting the plant from the river, Gulf Power officials say they also made it difficult for the plant to withdraw water from the river at an elevation lower than it is with at least 3.2 billion gallons of water a day flowing out of Woodruff Dam at Lake Seminole.

In the 1950s-era plant office, Gulf Power spokesman John Hutchinson says Scholz is critical to the overall reliability of the electrical grid serving the Florida Panhandle, southeast Alabama and southwest Georgia. Shutting it down to save water would increase stress on the rest of the system, he says.

Nevertheless, the utility, a sister company of Georgia Power, is looking for a long-term solution, assuming this drought continues into next year — or a worse one hits.

"We don't want to be in the position where we are the linchpin," Hutchinson said. "We know you have other considerations up and down the river. We're not taking a 'dig your heels in' kind of position at all."

Unlovable, yet essential

If more water doesn't start flowing soon past Plant Scholz and on downstream, digging in is exactly what the mussels may have to do to survive.

Last summer biologists moved about 800 mussels from a shallow pool to deeper water, but for all science knows, they may have fared better by staying put and burrowing deep into moist mud, waiting for the river to return.

These mussels are not creatures people love to love. The Native Americans ate them, but we don't. For the most part, they just sit in rivers and creeks.

But they perform critical functions as both filters — cleaning pollutants from the water — and food for raccoons, muskrats and river otters. Mussels are also a harbinger species, able to tell us as much or more about the health of our rivers than scientific tests and monitoring.

Out on the Apalachicola, Herrington shares the motorized jon boat with Gail Carmody, a veteran biologist and field supervisor in the Fish and Wildlife Service's Panama City office.

At a deep part of the river under a cypress tree, Herrington jumps into the murky water, squats and starts to feel around in the muck. What's she's looking for are four purple bankclimbers that she and other biologists had recently moved from shallower water. One by one, she plucks them from the water before carefully placing them back in their wet haven.

Still sitting in the boat, Carmody explains why scientists think they matter so much.

"They're part of the whole river system that both people and mussels depend on," she said as it starts to rain. "They're like the canary in the coal mine. We need to all work together to protect the mussels so we can protect people, too."

The biologists don't know whether this drought could drive the fat threeridge and purple bankclimber mussels into extinction. Three other species in the river basin already have disappeared.

"We're dealing with these unprecedented times. There's nothing to base this on," Carmody said. "The river's never been [this low] as far as we can tell."

Because of the high stakes, the Fish and Wildlife Service and corps are working together on an accelerated schedule to find out by mid-November just how much water the mussels need to survive. Until now, studying the mussels has taken place by wading into shallow pools and along the river banks in spots biologists have assumed they are most likely to be found.

Last week, divers started plunging into the river. If they find mussels in deeper water, it's more likely the species could survive if the river drops even lower.

The drought already has started changing the balance of the ecosystem. Ocean tides are overpowering the weakened river, pushing saltwater upstream for miles. Fishermen say they've spotted bull sharks swimming around Bloody Bluff Island, more than 15 miles upstream from Apalachicola Bay.

Joseph "Smokey" Parrish has worked in Apalachicola's seafood industry for 30 years.

He can taste a difference in the flavor of the oysters after even the slightest change in how much freshwater flushes through the bay. Crabbers are having to go farther upriver to make their catch. Shrimp have all but disappeared from the bay in the last year, he says, a major blow to Apalachicola Bay's $11 million seafood industry.

But mostly Parrish, a Franklin County commissioner, worries that the combination of continued drought and upstream withdrawals will permanently transform the bay, making it saltier and more hospitable to jellyfish than shellfish.

"It's not that people down here don't sympathize with what you're going through [in metro Atlanta]," he said. "But it's about a lot more than two mussel species."

Still, Parrish understands the realities of the Southeast's worst-known drought, boiled down to a simple fact:

"You can't give us more water than you've got to release."

For months, Lanier, more than 300 miles upstream, has been sending the Apalachicola billions of gallons more water than it otherwise would get if its only salvation was rain.

As a result, Lanier has dropped 5.5 feet since Sept. 1, and could drop to a historic low by the end of the year. State officials say metro Atlanta's water supplies could be jeopardized as early as January.

At their final stop on the Apalachicola River, next to a dilapidated fish shack, Carmody and Herrington show what could be the future of the muddy mussel graveyard just upstream. Last summer, the low-lying riverbank held enough water to keep hundreds of mussels alive. Now it's covered in dried-out vines and chest-high willow trees.

As she walks through the weeds, Herrington makes note of the casualty in this ecological change: "What's under your feet are a lot of shells."

ABOUT MUSSELS

Early Native Americans ate the mussels found in the Apalachicola River, but we don't. So what good are they?

• They serve as filters, cleaning pollutants from the water.

• They're food for raccoons, muskrats and river otters.

• They are a harbinger species. If they die off, it might be a sign the entire river is in danger.

• Freshwater mussels are related to snails and oysters.

• They eat plankton by drawing in water through a siphon and filter the waste out through gills.

• A muscular "foot" allows them to burrow in sand and move.

• Mussels reproduce by releasing fertilized eggs, called glochidia, into the water to attach to host fish. After a few weeks, the young mussel drops off the fish.

• Some species can live up to 130 years.

• Purple bankclimbers and fat threeridge mussels are no longer found in the Chattahoochee River, probably because of its dams.

Source: U.S. Fish and Wildlife Service