A dirty, rotten do-gooder Bog: Only Mother Nature, and biologists, could love the man-made haven for rare plants that fights pollution along the Severn River.

March 01, 1997|By Andrea F. Siegel | Andrea F. Siegel,SUN STAFF

It is the kind of mire nobody wants to fall into: percolating, mucky, pools of water spattered with clumps of moss, slime filling the gaps among rotting leaves, and an occasional haze above the water that hides the bugs.

The young Edge Hill Bog is gross, and it's supposed to be.

It is the first man-made bog created to remove pollutants and to provide a haven for rare plants. The first in the region, probably the first in the country, Keith Underwood of Annapolis, who designed it, said proudly.

"This is an innovation," said conservationist William Moulden, who helped create the seeping wetland in his waterfront Sherwood Forest community outside Annapolis.

All this has made the 10 soggy terraces at the edge of the Severn River a curiosity among the environmentally aware. Federal, state and local officials have visited since it was built last summer with $21,000 in Anne Arundel County funds and hours of volunteer labor.

What they have come to see is a seven-story ravine. Some 600 tons of sand and pebbles were poured into the bottom, which was terraced into graduated pools, each supporting different plants all feeding off the nutrient-rich water.

"Look at these as sponges," Moulden said about the sand and pebbles that act as bog filters.

The pools hold plugs of an array of plants from native cranberries, which absorb nitrogen, to threatened leatherleaf shrubs. Bushes and trees have been planted to prevent further erosion of the ravine's banks. Underwood said he tried to keep to plants that grow around the Severn or once did.

A dozen Atlantic white cedar saplings poke out of the landscape. These towering cedars were a dominant species in the coves around the river until Colonial shipbuilders stripped the area. At a sturdy 130 feet tall, they made great masts.

The adventurous can tour the half-acre bog atop slabs of fallen trees that have sprouted earlike fungi and make a curving path through the ponds.

What look like swirls of motor oil on the water really are something healthy: Leptothrix discophora, manganese-fixing bacteria that enjoy a good bog.

"It means he has one that is working. This is independent confirmation -- because the bacteria don't read the book," said Eleanora Robbins, bio-geologist with the U.S. Geological Survey and a specialist in such microbes.

Just how well the low-tech solution to pollution is functioning no one knows for sure yet. This first full growing season will be a key test to see if the cranberries thrive and form scarlet-berried mats. But one thing is sure, the artificial bog already is keeping nitrogen out of the river.

Scientists know that wetland plants absorb nitrogen, but only recently have they explored using them as biological filters.

Underwood said his tests show 80 percent of the nitrogen is being filtered out of the 5 gallons a minute of surface water that dribbles into the river.

But geology professor Eileen McLellan said preliminary ground water tests run by one of her University of Maryland College Park students show "more like a 20 percent reduction." She also questioned how well the plants are doing.

The bog will get better as it gets older, said Underwood. The pools will become more acidic -- more boglike -- as white-beaked rush decays into peat, Underwood said.

"Five to 10 years from now, you won't see the terracing. You will see only vegetation," Moulden predicted.

In May, a second round of planting will start. Underwood and his minions will add three or four kinds of threatened orchids, endangered swamp pinks and insect-eating pitcher plants, all increasingly rare as natural bogs are vanishing.

"They are very vulnerable to the changes made by residential development due to the runoff you get," said Katharine McCarthy, Southern regional ecologist for the state Department of Natural Resources' Heritage and Biodiversity Conservation programs.

Bogs are always wet but not flooded, acidic and low in nutrients. Only a specialized group of plants tolerate such stressful conditions, McCarthy said.

Those plants, and the soggy environment, attract a specialized LTC set of animals, too. On the theory that if you build it, they will come, the bog should draw the cranberry moth, on the state's endangered list, and salamanders, Moulden said.

Septic systems from 25 houses, most with plumbing that predates the Great Depression, drain into the ravine. So does runoff from a few acres of Sherwood Forest's golf course, which is kept green thanks to 1 ton of fertilizer a year. Before the terraces were built, that runoff poured directly into the Severn River.

The heavy nitrogen load from runoff leads to massive growth of algae, which then blocks sunlight, cuts water clarity and ruins the river for other plants and fish.

But cranberries in the bog use up nitrogen.

Even a 20 percent reduction in nutrients might be valuable, said Thomas C. Andrews, Anne Arundel County land use officer, because it is half the state's goal.

Maryland, Pennsylvania, Virginia, the District of Columbia and the federal government pledged in 1987 to restore the bay's water quality by reducing nutrient pollution 40 percent by 2000. Controlling the amount of nitrogen that drains into waterways from runoff, or nonpoint, sources is crucial.

The usual way to do that is to build multimillion-dollar water treatment plants. So officials will be avidly watching the performance of the inexpensive little bog over the next few years.

Pub Date: 3/01/97

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