A recent survey of underwater seagrass abundance in Maryland’s coastal bays shows the plants have decreased by 35 percent in less than year. The study, released by the Maryland Department of Natural Resources (DNR), the Maryland Coastal Bays program, the Virginia Institute of Marine Scientists and the National Park Service, showed underwater grasses dropped from 13,863 acres in July 2010, to 9,083 acres in May 2011.
The loss of submerged aquatic vegetation during 2011 was more extensive than during the hot summer of 2005 when 4,780 acres lost in Maryland's coastal bays throughout the area.
Chincoteague Bay lost 2,756 acres of seagrasses. The northern bays showed the greatest percent losses: Assawoman Bay saw a 96 percent decline, or 900 acres; the Isle of Wight, 93 percent or 483 acres; and St. Martin River lost its last 1.6 acres.
Seagrasses are an important indicator of clean water and serve as food and shelter for many fish and shellfish, including flounder, blue crab and bay scallops. The plants are also a vital food source for Atlantic Brant and other waterfowl during migration and over-wintering.
Scientists cite low water quality as the greatest threat to seagrass recovery. When nutrients enter coastal bays, algae and seaweed blooms often occur, blocking light to seagrass beds. Sources of nutrient pollution include air deposition, farm fields, boating, development, septic fields, parking lots, and wastewater treatment plants.
“Maryland is among the states most vulnerable to climate change. Hotter summers and rising sea levels, along with increased storm intensity, could have devastating and far-reaching environmental and economic impacts on the Coastal Bays ecosystem and the quality of life Marylanders currently enjoy,” said Zoe Johnson, DNR Program Manager for Climate Policy. “The seagrasses are a great barometer of the health of the coastal bays. We must continue to reduce nutrient and sediment pollution, collectively and individually, to benefit seagrass restoration and ultimately the health of the coastal bays.”
Although eelgrass in Maryland’s Coastal Bays and in the upper Chesapeake Bay have declined, Virginia’s coastal bays have continued to produce the important plant. According to Dr. Bob Orth, who oversees the annual SAV monitoring surveys, "the clearer water of the Virginia coastal bays, as well as the proximity of the eelgrass meadows to cooler ocean waters makes the exposure to stressful high water temperature conditions more bearable, allowing these meadows to persist despite the high summertime temperatures."
Long-term monitoring by Assateague Island National Seashore shows current trends in nutrient conditions continue to degrade in Chincoteague Bay. However, there are some promising signs of improvements shown by data collected by Maryland Department of Natural Resources, especially in Kitt’s Branch/Trappe Creek, as a result of removing wastewater discharge from Berlin.
Seagrass acreage is estimated through an annual aerial survey, which is flown between late spring and early fall. Additional information about the aerial survey and survey results is available at www.vims.edu/bio/sav/.
source: MD DNR