Chesapeake Bay grasses suffered their worst decline in 20 years after a torrent of rains last spring and summer washed huge amounts of sediment and nutrients into the water, according to a report released yesterday.
The findings, which come from the Virginia Institute of Marine Science's study of submerged aquatic vegetation in the bay from May to October last year, show that the grasses decreased 30 percent throughout the tidal bay, and 41 percent in Maryland. The report marks a setback for the multistate push to restore the grasses -- and with them crab and fisheries habitats -- by 2010.
"It's very unlikely we're going to meet our restoration goal," said Mike Naylor, an environmental specialist at the Maryland Department of Natural Resources who has been examining the health of submerged aquatic vegetation. "This decline reveals how easily we are set back a decade in progress just by a single bout of bad weather."
Bay grasses are not only a critical habitat for juvenile fish and crabs, which hide in them to escape predators; they are also an indication of the water quality across the bay. The grasses protect the shoreline from erosion and increase the bay's oxygen supply.
Aerial photographs indicate that bay grass acreage in Maryland dropped to 30,990 acres last year, a significant decline from the 52,546 acres in 2002.
For the whole Chesapeake region, the numbers are 64,709 acres last year compared with 89,659 in 2002.
Scientists said the study did not capture the full effect of Tropical Storm Isabel on the grasses, which is still being measured.
Last year's figures fall far short of the federal-state bay restoration program's goal to reach 185,000 acres by 2010.
The picture is all the more disappointing, biologists say, because the drought years of 2001 and 2002 were good ones for the bay grasses. With fewer nutrients bringing algae to cloud the water, the grasses soaked up sunlight and bloomed with a vigor not seen in years.
During the drought, Chesapeake Bay Foundation President Will Baker warned that the grass comeback was only temporary, and that pollution would flow back into the bay and its tributaries when the rain returned. Yesterday's numbers, he said, bear that out.
"The grasses are just the canary in the mine shaft," Baker said. "They're an indication of a problem we need to be very aware of and address before the loss of fisheries and other things occur."
The middle Chesapeake Bay region, which stretches from the Bay Bridge to the Rappahannock River and Pocomoke Sound, suffered the worst decline, with a 41 percent drop.
Peter Bergstrom, a fisheries biologist with the National Oceanic and Atmospheric Administration in Annapolis, said the middle bay's poor performance stems from its lack of grass diversity.
While Bergstrom said the losses erode what was gained in 2002, he sees some encouraging signs that Maryland is focused on restoration. The so-called "flush tax" will raise close to $1 billion for upgrading sewage-treatment plants and replacing some outdated septic systems.
"We can't control rainfall, so we have to control how much runoff comes during the rainfall," he said.