Heavy spring rains, a hot summer and two major storms caused the Chesapeake Bay's overall health to worsen last year, scientists said Tuesday, though there apparently was a slight improvement in the Baltimore area's Patapsco and Back rivers, long considered among the bay's most degraded tributaries.
The beleaguered bay saw its ecological grade slip from a C- in 2010 to D+ last year in an annual report card drawn up by the University of Maryland and the National Oceanic and Atmospheric Administration. It was the second decline in as many years, with North America's largest estuary getting its second-worst health score, 38 percent, since scientists began making annual assessments in 1986.
"It could have been worse … at least we're not failing," said William Dennison of UM's Center for Environmental Science, who oversees the annual checkup.
Dennison said unusually unfavorable weather last year, capped by Hurricane Irene and Tropical Storm Lee in late summer, overpowered whatever improvements might have been seen from bay watershed states' efforts to reduce the pollution fouling the Chesapeake's waters.
Spring downpours washed more nutrients and mud into the water, while a dry, hot summer spurred algae blooms and increased the size of the bay's oxygen-starved "dead zone." The hurricane, followed by the tropical storm's torrential rains, turned the upper bay a milky brown with sediment.
Water clarity was the worst it's ever been, continuing a long-term decline that Dennison said scientists are at a loss to explain. There was also a large decline in the underwater grasses that provide shelter and food to fish and crabs, though he said the bay's crab and striped bass populations remained strong.
Dennison said scientists and environmental officials believe last year's decline was a temporary setback that shouldn't prevent the bay's gradual rebound as Maryland and other bay states increase their pollution reduction efforts.
"We know we're going to continue having these kinds of events," said Nicholas DiPasquale, director of the Environmental Protection Agency's Chesapeake Bay office in Annapolis. "Mother Nature's somewhat fickle and can give us a head slap once in a while."
But DiPasquale pointed to a recent study by scientists from the Johns Hopkins University and UM that found the bay's water quality trending better over the decades, despite annual ups and downs.
"The nutrient reductions that have taken place are showing some results," the EPA official said. With bay watershed states finalizing plans to meet EPA-set pollution goals by 2025, DiPasquale said he was confident the bay's condition would continue to gradually strengthen.
Dennison pointed to "bright spots" in last year's overall decline that he said showed the estuary's growing resilience now in the face of natural insults.
For instance, while eel grass beds farther down the Chesapeake suffered from the water's diminished clarity, Dennison noted that the grass beds in the lower Susquehanna River appeared to have been relatively unscathed by the deluge of mud the tropical storm washed into the bay from Pennsylvania.
Also, the rivers and creeks along the Anne Arundel County shore and in the Baltimore area — two regions of the bay that have consistently fared poorly — showed signs of improvement last year.
The Patapsco and Back rivers saw their health grade rise from a worst-in-the-bay F in 2010 to D- last year. Dennison said scientists detected more small shellfish, worms and other aquatic life on the bottom than in years past, and a healthier mix of algae in the water. He cautioned, though, that the sampling of the two rivers had been fairly limited, so might not reflect their overall condition.
"It may be on life support, but it's not deteriorating," he said of the two rivers' status.
Still, any sign of improvement was welcome news to activists working to clean up sewage leaks and overflows and storm runoff fouling Baltimore's harbor.
"It's always good to see an uptick," said Halle VanDerGaag, executive director of Blue Water Baltimore. "It shows that improvements can be made," she added in an email, concluding that "it would be wonderful if this was the beginning of an upward moving trend."
Two other bay tributaries received failing grades in the new report card, Maryland's Patuxent River and Virgina's Elizabeth River in Norfolk. Dennison said the Patuxent, which flows from Central through Southern Maryland, shows troubling signs of decline, while the Elizabeth, with a legacy of pollution from a naval base, shipyards and industry, earned scientists' worst grades.