by Alicia Pimental
June 01, 2006
Underwater bay grass acreage increased by seven percent in 2005 to a total of 78,260 acres, according to data gathered by the Virginia Institute of Marine Science for the Chesapeake Bay Program. The 2005 acreage represents about 42 percent of baywide restoration goals.
While this increased acreage is encouraging, scientists are concerned about possible losses in 2006 due to a widespread defoliation of eelgrass in lower and mid-bay areas. This occurred after last summer's unusually high water temperatures and calm conditions. The full extent of the losses will not be known until June, when the aerial survey of key areas is completed.
Abundant bay grasses are essential for a thriving Chesapeake Bay ecosystem. Bay grasses reduce pollution by absorbing nutrients and trapping sediments and provide shelter and nursery areas for juvenile striped bass and crabs.
The Bay has seen a slow increase in bay grass coverage, from 38,000 acres in 1984 to nearly 90,000 acres in 2002. Because of the importance of bay grasses to the Bay ecosystem, the Bay Program partners have committed to protect and restore 185,000 acres by 2010.
Bay Program partners are working to provide optimal water quality conditions for bay grasses by upgrading sewage treatment plants, planting streamside forest buffers and minimizing runoff from developed and agricultural areas. Water clarity improvements are critical to helping the Bay's underwater grasses return to their former abundance.
Some 19,464 acres of underwater grasses were mapped in 2005. While about ten percent lower than last year's record level of 21,673 acres, the average density of the beds increased, providing higher quality habitat for resident aquatic life. The density of grass beds in this area has been steadily increasing since 1999, following almost 15 years of sparse coverage. Bed density has almost tripled since 1999, increasing from about 1,700 acres to nearly 5,000 acres of moderate- to high-density beds in 2005.
Last year's 39,576 acres marked a 17 percent increase, but is far below the previous high of 52,971 acres in 2002. Bay grass acreage in this region is dominated by widgeon grass, a species that shows tremendous inter-annual variability. The middle bay has seen two peaks since 1984, one in 1992-93, and one in 2001-02.
Below the Maryland/Virginia state line, grasses covered 19,220 acres in 2005, a nine percent increase from the unusually low acreage recorded in 2004. After a period of steady increase from 1984 through 1993, bay grass abundance in this region has fluctuated, generally averaging of approximately 21,000 acres. Changes observed between 2004 and 2005 in some areas of the lower and mid-bay were likely a result of these beds beginning a recovery from the effects of Hurricane Isabel in 2003.