One small waterway on the Potomac River shows that cleanup efforts can work
— with enough time.

Underwater grassbeds, like this patch of Eurasian watermilfoil (Myriophyllum spicatum), have come back in Gunston Cove. The water is clear enough for grasses to survive again, the result of upgrades to a water treatment plant nearby and long-term efforts by activists. Photograph by Michael W. Fincham; map, iStockphoto.com/University of Texas Map Library.

ROB HARTWELL'S CHILDHOOD was, in a way, vintage Mark Twain. He grew up on Mason Neck, a small peninsula on the Potomac River in Virginia. Located about 20 miles south of Washington, D.C., the neck forms the southern border of a narrow bay called Gunston Cove. "My idea of an ideal day was to walk a mile or two down the river bank at low tide and see how many snakes I could find," says Hartwell, who still lives near the banks of that cove today.

But it was Mark Twain with a twist. Many days, he'd have to play on the opposite side of the neck because dead fish had piled up along Gunston Cove — likely the victims of poor water quality.

Then there was the home movie he watched over and over again. Shot by his mother on an eight-millimeter camera, the film showed one of their neighbors climbing out of the water off Mason Neck after a swim. He was covered in green slime. "He looked like the creature from the black lagoon," says Hartwell, who today is a Virginia commissioner for the Interstate Commission on the Potomac River Basin, a government group that advocates for the Potomac.

The troubles facing Gunston Cove, which stretches about two-and-a-half miles long and reaches widths of more than three-quarters of a mile, came down to how the region dealt with sewage. A few miles upstream from this cozy cove on a tributary called Pohick Creek sat a wastewater treatment plant — now called the Noman M. Cole Jr. Pollution Control Plant. And every day, this facility, which was built in 1970, pumped tons upon tons of treated wastewater right toward Hartwell's old stomping grounds. That wastewater, in turn, was loaded with phosphorus.

And that was a problem. Microbes need phosphorus to survive, but in freshwater ecosystems like this one, this nutrient tends to be harder to find than others, such as nitrogen. The sewage plant's discharges fed the algae's craving for phosphorus, and the microorganisms — particularly, a class of microbe called cyanobacteria or blue-green algae — feasted, growing out of control. In the deeper waters of the Potomac, such "blooms" even led to decreases in the oxygen dissolved in the water column, suffocating schools of fish. The region became known for its fish kills and for generally bad water quality. "It was notorious," Hartwell says.

In many senses, Gunston Cove's story mirrored the stories of tributaries up and down the Chesapeake Bay watershed: never-ending algae blooms and chronically poor water quality. But that notoriety also inspired change. By the early 1980s, a multistate and federal effort to clean up the Bay was beginning to organize, and its target was excess nutrients.

On Gunston Cove, change began early on in that drive. Responding to citizen concerns, Virginia's Fairfax County, which oversaw the plant, opted to upgrade its treatment technology. The work was finished by 1980. The plant's operators built new settling tanks and filters to dispose of phosphorus waste. Elsewhere, treatment plant operators around the Bay completed similar overhauls. The Fairfax County plant managed to winnow out around 85 percent of the phosphorus it was sending downstream toward Gunston Cove. But, by the next summer, the cove was no less green with algae. Nor was it the following year. Or the year after that.

"They made a strong management action. They invested a lot of public money, and they did what they thought was right. And the response was zero," says Walter Boynton, an ecologist at the Chesapeake Biological Laboratory of the University of Maryland Center for Environmental Science. "They had to wait."

Years later on Gunston Cove, Christian Jones pulls a clawlike tool called a Ponar grab up out of the water and onto his small sport-fishing boat. He dumps its contents into a bucket — globs of dark grey mud. He also finds a single sprig of bay grass. Jones, an ecologist at George Mason University, holds the plant in the palm of his hand. It's thin, leafy, and still wet. Hydrilla, he calls it, talking to a half dozen college students crammed in around him.

The scene is quiet this morning. The water is smooth, and what few waves there are barely jostle our boat. The students are here with Jones to learn how scientists like him gauge the health of freshwater rivers and bays. And that's where the hydrilla comes in.

Holding up a clump of healthy bay grass, Rob Hartwell can smile about the Gunston Cove recovery. He remembers when Gunston was empty of grasses and covered with green slime. As a longtime advocate, he's worked to keep this cove healthy. He currently serves on the Interstate Commission on the Potomac River Basin. Photograph by Michael W. Fincham.

The small plant says a lot about the health of Gunston Cove. Hydrilla, or Hydrilla verticillata, isn't native to the region, but it has been able to colonize rivers up and down the estuary since its introduction from Florida in the 1980s, providing habitat for native fish and other animals. That's important because underwater vegetation like this has been disappearing all over the Chesapeake Bay — plagued by deteriorating water quality. But here, bay grasses, even native ones, are flourishing. Much of the river bottom stretching out around us is covered in the stuff, Jones says in his casual, southern accent: "They're just below the surface right now." In other words, the cove today is not the same algae-choked waterway that Hartwell remembers from his youth — then, only a thin fringe of plants grew along the Mason Neck shoreline.

Other waterways, including the Potomac itself, have shown similar improvements in water quality, going from unswimmable to swimmable — or, at least, slightly less prone to fish kills. But few, if any, waterways the size of Gunston Cove have made such a stark turn-around. Still, the cove's story comes with a caveat: every river and Bay may take different times to recover.

"I think it's a good lesson that we're dealing with a complicated ecosystem," Jones says. "While we understand the basics of how it works, we don't know it well enough to know exactly when our management efforts are going to kick in or pay off."

Jones spent a lot of time waiting for that payoff. He's monitored the health of Gunston Cove with funding from Fairfax County since 1984 and has long been fascinated by freshwater communities, especially their microscopic members. Even today, the Arkansas native brings home a jar filled with water every time he travels to the cove — which is often. He puts the sample under his microscope and looks for the tiny animals, bigger than algae but too small to see well with the naked eye, swimming or just floating around. "I always find a wonderful thrill looking at microorganisms," he says.

Many of those animals and many larger ones (fish) do best when there are thick beds of bay grass around. But when Jones first began his studies, Gunston Cove was still very much the domain of the creature from the black lagoon. The situation got so bad that in 1983, the Metropolitan Washington Council of Governments invited a team of international experts on water quality to the region to discuss one topic — why wasn't the cove getting better?

Here's what they concluded: the faucet supplying Gunston Cove with large amounts of phosphorus had been effectively cut off, but algae there were still thriving off a huge reserve — and it lay just below the surface. Phosphorus molecules, by virtue of their chemistry, tend to bind to grains of dirt and silt. Those grains also sink, meaning that the mud at the cove's bottom was likely chock-full of the nutrient. And bit by bit, all that phosphorus was trickling back up into the water column. The theory was supported by observations taken later by Jones and his colleagues.

But there was good news, too. With enough time, all that phosphorus would likely be used up, washed away, or trapped under another layer of sediment. In other words, there'd be no more available for the algae. All Jones needed to do was wait.

The water quality in Gunston Cove never improved in one big leap. No single moment arrived when the scientists clinked champagne glasses, Jones says. Things just got better — slowly but surely. "By 1995, we weren't seeing the big algal blooms anymore," he says. "By 2000, it was obvious that not only were the blooms not occurring, but the average amount of algae was going down." Those changes built on top of each other, eventually clearing the way for bay grasses. Today, underwater plants, like watermilfoil and the hydrilla Jones found, cover about 40 percent or more of the cove bottom.

The net result is that Gunston Cove is now usually a lot less green with algae than the Potomac. It's a role reversal for the two bodies of water. "A lot of times, the cove is clearer than the river channel," Jones says. "And that would have never occurred before." Part of the difference lies in the fact that the Potomac, like much of the Bay watershed, also picks up a lot of nutrients from the fertilizers used on nearby farms. Gunston Cove, however, is relatively isolated from agricultural land. Still, for many, the inlet shows that, with enough time and effort, ecosystems like this one can regain some of their lost health and diversity.

"I love Gunston Cove because it's that magic little story that says if you do the right things, [a waterway] will heal itself," says Stella Koch, who works to conserve streams for the Audubon Naturalist Society.

That's a relatively new way of looking at river restoration. For years, scientists assumed that it might take generations to clean up waterways like Gunston Cove. But while it's clear today that you'll have to wait, you won't have to wait forever, says Walter Boynton who's studied ecosystems like these for decades. When he was a young student, "the view of estuary recovery followed the theme: we have been enriching these estuaries for...hundreds of years, and therefore it will take a similar time for restoration," Boynton says. Now, he can say, "that just doesn't seem to be true."

Christian Jones looks at a water sample filled with small crustaceans called copepods, taken from the water near the mouth of Gunston Cove. An ecologist at George Mason University, he collects small organisms for fun and uses a microscope to photograph them, often posting the pictures on his team’s website. Photograph by Daniel Strain.

Gunston Cove isn't the only proof of that, either. The Potomac also cleared up in the 1980s after the nutrients spilling into it from a wastewater treatment plant in Washington, D.C. were cut. The Back River, which runs through northern Baltimore, offers an even newer example. In 1998, the operators of a sewage plant on this famously polluted waterway reduced the nitrogen discharged by the facility. Within three years, measures of algae in the river had been halved.

By comparing ecosystems like these, Boynton's seen that separate bays and rivers may recover at different speeds. The pace of change, he says, likely comes down to a number of factors, such as how efficient ecosystems are at storing nutrients. But for a scientist who's spent much of his career studying the Bay's decline, such recoveries are a welcome sign.

"It is kind of delightful at this stage of life to study issues of restoration, which are significantly more positive," he says.

Still, both Boynton and Jones say that restoration can't bring back the past. Both scientists doubt that Gunston Cove will ever return to how it was during the dawn of the United States — when, according to reports, one local landowner used to string a 350-foot-long seine net across the Potomac not far from the cove, catching tens of thousands of shad each year. Even when natural resource managers and scientists succeed in restoring waterways like Gunston Cove, "very seldom do they go back to the same system because so many things are off in so many ways," Jones says.

Rob Hartwell, however, is happy all the same. Algae or no, he's gone swimming around Mason Neck every year, much like his neighbor covered in slime. But these days, he can open his eyes underwater — a benefit of having fewer microbes around. There's still a lot work to be done, he says, but today, the region is an "oasis close to Washington." It's one where that old sea monster captured on an eight-millimeter camera won't be visiting anytime soon.