Virginia Institute of Marine Science Bay Grass Survey Shows Improvements

The latest Virginia Institute of Marine Science Bay Grass Survey shows that the abundance of underwater grasses in Chesapeake Bay increased by 18 percent last year, from 64,917 acres in 2007 to 76,861 acres in 2008.

This is the fourth largest total acreage of bay grasses recorded since the bay-wide survey began in 1984. Bay grasses increased in abundance in several areas.

Maryland waters had a 12% increase, the second highest level seen in Maryland waters since the Virginia Institute of Marine Science began its annual bay grass survey in 1984. The 12 percent increase in Maryland’s portion of the Chesapeake Bay and its rivers brings the State to 41 percent of its bay grass restoration goal. Maryland’s bay grasses totaled 47,286 acres in 2009, up from 42,237 acres in 2008.

In addition to increased bay grasses, the Chesapeake Bay’s blue crab population has increased substantially for the second straight year. The latest winter dredge survey shows a 60% increase in Maryland’s crab population.

“Because bay grasses are sensitive to even small changes in water pollution, they serve as a key indicator of Chesapeake Bay health,” explained Maryland Department of Natural Resources Secretary John Griffin. “Healthy bay grass beds protect shorelines from erosion, produce oxygen and filter polluted water.”

Grasses on the Susquehanna Flats, near Havre de Grace, have quadrupled since the early 1990s, and a single bed now covers approximately 12.5 square miles, the largest in the Bay. Other improved areas include the upper Potomac River, from the Woodrow Wilson Bridge south to Mattawoman Creek.

Bay grasses in the middle section of the Chesapeake Bay, the area south of the Bay Bridge to the Virginia state line, also increased including areas located on the lower Eastern Shore and in Tangier Sound near Smith Island.

Growth of eelgrass, along with widgeon grass, accounted for about 60 percent of the baywide increase. These notable gains include 1,337-acres (11%) in the Tangier-Smith Island region, 1,092-acres (9%) in the eastern lower Chesapeake Bay and 1,794-acres (29%) in Mobjack Bay. Widgeon grass showed a very strong resurgence in the 2,985-acre increase (24%) in the Honga River.

While healthy bay grasses expanded in the upper Chesapeake Bay and on the Eastern Shore, several rivers on the middle Western Shore experienced bay grass declines.

The Magothy River, near Annapolis, and Piscataway Creek, in the upper Potomac River, both lost over half of their grasses in 2009. Bay scientists are working to understand the causes of these declines in order to better target restoration efforts in these rivers.