Rains deliver fresh blow to bay cleanup Storms, snows of '96 foul Chesapeake with sediment, algae

'We need a normal year'

River-fed pollution could affect grasses, oysters, other species

July 07, 1996|By Timothy B. Wheeler | Timothy B. Wheeler,SUN STAFF

Heavy rains and snow melt have flooded the Chesapeake Bay, fouling it with nutrients and sediment, spurring record algae blooms and risking at least a temporary setback in its improving water quality.

The deluge could worsen the "dead zone" that chokes the deep waters of the bay each summer and could deal another blow to the estuary's struggling underwater grasses and oyster population.

Experts differ over how -- or even whether -- blue crabs and fish might be affected by the weather-related phenomenon.

"We'll see how it translates to the critters this fall, I guess," said Karen Bisland, a biologist with the U.S. Environmental Protection Agency's Chesapeake Bay program office in Annapolis.

The bay's tributaries poured almost 56 billion gallons of water daily into the Chesapeake last month, a flow more than one-third higher than normal for June, the U.S. Geological Survey reported last week.

That freshwater inundation, the sixth-highest recorded for June, comes on the heels of near-record rivers flows in May and a record outpouring in January after heavy snowfall, the survey said.

"The high flows bring increased nutrients and sediment to the Chesapeake Bay," said Scott Phillips, a USGS hydrologist.

"We had some pretty big cloudbursts," acknowledged Robert E. Magnien, director of tidewater ecosystem assessment for the Maryland Department of Natural Resources. "That affected a lot of local waters."

The nutrient pollution comes from the air and from nitrogen and phosphorus -- in the form of sewage, fertilizer and animal waste -- washing off land in the bay's extensive watershed. The bay states have pledged to reduce nutrient pollution by 40 percent by the end of the decade.

The flows already have had one measurable result -- record blooms of algae, the microscopic plants whose growth can worsen the bay's water quality.

"I haven't seen anything like it," said Lawrence W. Harding Jr., an oceanographer with the University of Maryland who has been conducting aerial surveys of algae blooms in the bay since 1989. The algae blooms stretched to the Atlantic Ocean.

Record freshwater flows early this year coupled with snowmelt "loaded the bay up with nutrients," Harding said, producing some of the earliest and most extensive algae blooms he's seen.

"When we first began flying in March, we had red tides [algae] in and around the Bay Bridge and up toward the Patapsco River," he recalled. During spring, the midbay was clogged all the way to the Virginia capes with brownish-looking blooms, he said.

The first wave of algae growth started to die back in April, until a series of windy storms churned up the bay and revived the microscopic aquatic plant growth.

"It's like your garden," he said, where turning over soil likewise encourages plant growth.

Algae blooms contribute to the bay's water-quality problems by clouding the water, blocking sunlight needed to sustain underwater grasses. When algae die, they sink to the bottom, and their decay consumes oxygen in deep water, creating an unwholesome "dead zone" for fish and shellfish.

Harding said he expected the bay's water to be "severely anoxic," or lacking in oxygen, this summer, but more because of the volume of fresh water than because of extra algae. Lighter freshwater flows over the heavier saltwater coming in from the ocean, creating layers that do not mix well, depriving bottom waters of oxygen.

The flows also could hurt the bay's underwater grasses, which had been slowly returning after a major die-off in the 1970s and early 1980s. Last year, the crucial nursery grounds for the bay's fish and crabs shrank by 8 percent from the year before. It was the second straight decline, which scientists pointed out came after heavy freshwater flows into the bay in 1993 and 1994.

Even with the recent declines, bay grasses have expanded overall by almost 60 percent since their low point in 1984. However, these weather-related fluctuations are "Mother Nature's way of reminding us that our job is nowhere near done," said Robert Orth of the Virginia Institute of Marine Science, who directs bay grass surveys.

The extra nutrients could be a mixed blessing for the bay's

crabs, fish and oysters. Nutrients provide food for microscopic plants and animals, which in turn serve as food for larger marine life.

Edward Houde, a fisheries biologist at the University of Maryland's Chesapeake Biological Laboratory, said there appeared to be plenty of small crabs in the bay, despite the extremely low catches recorded in April and May.

Oysters could get some respite from the parasitic diseases that have devastated them in recent years, as the organisms -- MSX (( and Dermo -- fare better in salty water. However, oysters also need saltier water to reproduce well, and they can suffocate if their water turns fresh for an extended period in warmer weather.

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