More than a third of Maryland coastal bays' sea grass beds disappeared last year, a state survey has found, wiping out nearly 20 years of recovery in vital underwater vegetation in the shallow, fragile estuaries.
The survey, done by the Department of Natural Resources, the Maryland Coastal Bays program, the Virginia Institute of Marine Scientists and the National Park Service, found underwater grasses shrank from 13,863 acres in July 2010 to 9,083 acres in May of last year.
The decline to levels not seen since the early 1990s is being blamed on degraded water quality as a result of nutrient pollution and an extremely hot summer in 2010, which earlier had been linked to underwater grass die-offs in the lower Chesapeake Bay.
"These losses are troubling to the recovery of the bays,” Dave Wilson, executive director of the Coastal Bays program, said in a DNR press release. "We have lost nearly 20 years of seagrass recovery and the primary nursery for crabs and fish along with it."
Chincoteague Bay, which straddles the Maryland-Virginia border, lost the most grasses, 2,756 acres' worth. But to the north, Assawoman and Isle of Wight bays both lost more than 90 percent of their underwater vegetation, while the severely stressed St. Martin River lost its last 1.6 acres, the survey concluded.
While Maryland’s coastal bays and the Chesapeake are losing eelgrass, it's growing in Virginia’s coastal bays. Bob Orth of VIMS, who oversees the annual bay grass survey, says that may be because the water is clearer in Virginia's bays, giving underwater vegetation more sunlight, and because heat stress there may be moderated by the proximity of cooler water from the Atlantic Ocean.
Long-term water-quality monitoring by Assateague Island National Seashore shows nutrient pollution worsening in Chincoteague Bay, though DNR officials say conditions are picking up some in a couple tributaries, Kitts' Branch and Trappe Creek, since wastewater discharge from the town of Berlin was eliminated.