Chesapeake Bay fouled by Susquehanna flooding
Runoff from Tropical Storm Lee threatens grasses, may create dead zone
DNR biologists Zofia Noe and Jamie Strong stop off Rock Hall to record data from water monitoring devices. Noe is holding a device that measures light attenuation. They are sampling five sections of the Chesapeake Bay. (Kim Hairston, Baltimore Sun / September 15, 2011)
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Braving boat-damaging hazards, scientists are swarming over the bay to see if the massive stormwater runoff from Tropical Storm Lee last week is going to knock the troubled estuary for another loop, just as it was recovering from an especially rough summer.
"It just doesn't look right," Jamie Strong, a biologist with the Maryland Department of Natural Resources, said of the malted-milk hue of the water as he and state biologist Zofia Noe cruised north from the Bay Bridge on Wednesday to sample water conditions. Along the way, they dodged partially submerged tree trunks — not always successfully — and skirted sprawling mats of grass and trash atop the water.
What they found on a five-hour run along the Eastern Shore to Tolchester and back was water so murky you couldn't see more than a few inches deep. And the water was and almost completely fresh, at least at the surface.
Those and other byproducts of the storm pose serious threats to the underwater grasses that provide shelter for fish and crabs, and to the bay's struggling oysters, already so depleted by overfishing and disease that a scientific study recently called for a moratorium on harvesting the remaining ones.
"It just breaks your heart," said William Goldsborough, senior fisheries scientist with the Chesapeake Bay Foundation, who made his own post-storm reconnaissance earlier this week. "It's like a war zone out there. You can't help but think we've just taken a big giant step backwards in the health of the bay."
The torrential rains from Tropical Storm Lee flooded the Susquehanna River, the bay's largest tributary. The river's flow hit near-record levels on Friday, peaking at 778,000 cubic feet per second pouring through Conowingo Dam, according to the U.S. Geological Survey.
Scientists have reason to worry about such floods harming the bay. The Susquehanna's highest flow ever, 1.1 million cubic feet per second, came after Tropical Storm Agnes in June 1972, a monster rainstorm that scientists say devastated a seriously ailing bay. Underwater grasses and oyster and clam beds were smothered by a blanket of sediment, and some have not recovered.
Last week's storm fell well short of that apocalypse, but still washed more mud, debris and pollution into the bay than has been seen from one storm in years.
Swollen by rainfall first from Hurricane Irene and then Tropical Storm Lee last week, the surging Susquehanna sent enough fresh water into the bay to completely replace all the water in it, according to Mark Trice of the Department of Natural Resources.
Even if crystal clear, fresh water can stress and kill oysters and clams, which normally grow in brackish or salty water.
The USGS also estimated that the roiling Susquehanna scoured 4 million tons of sediment trapped behind Conowingo and other dams on the river and carried them downstream.
Agnes, by comparison, dumped five times as much silt and mud into the bay. Even so, the bay's water Wednesday was so murky that a disk used to test clarity vanished within a few inches of the surface. Normally, Strong said, you could see down at least a foot or two.
Also worrisome are the invisible pollutants. The rainfall running off streets, parking lots and farm fields flushed untold amounts of fertilizer, animal manure and other organic matter into the bay and its tributaries. Hundreds of millions of gallons of diluted but raw sewage also spilled into rivers and creeks as rains and rising waters overwhelmed municipal wastewater treatment systems. Spills of millions of gallons were reported in Colgate Creek, Baltimore, the Patapsco River and other area streams.
All of those materials contain nitrogen and phosphorus, nutrients which help plants grow on land, but feed water-fouling algae blooms in the bay. Massive algae growths every spring set up the oxygen-starved "dead zone" that forms every summer in the bay.
"With all this nitrogen and phosphorus coming into the system, you can't but have an impact on it," said Richard Batiuk, associate director of the Environmental Protection Agency's Chesapeake Bay office in Annapolis.
This summer's dead zone, aggravated by an extra dose of nutrients during an unusually wet spring, was perhaps the largest since scientists began tracking them more than 25 years ago.
Hurricane Irene, which blew through the region the week before last, actually helped break up the bay's dead zone, scientists say. Its winds stirred up the water, mixing oxygen back into the depths, and the storm's rains, though intense, weren't as severe or prolonged as feared. But the new flush of nutrients and fresh water from Tropical Storm Lee may trigger formation of a new dead zone, scientists say.
If a dead zone forms this fall, scientists say they don't expect it to grow as large as it was earlier this year. The storm last week came near the end of summer, when gradually declining temperatures slow the growth of algae in water. Agnes, by comparison, hit in June, when grass beds are growing and when algae blooms begin to form.