by Alicia Pimental
April 16, 2008
Underwater bay grasses covered nearly 65,000 acres of the Bay and its tidal rivers in 2007, about 35 percent of the 185,000-acre baywide restoration goal. Though a 10 percent increase from 59,000 acres in 2006, bay grasses have not yet recovered to the recent high of 90,000 acres in 2002.
In the upper Bay zone (from the Chesapeake Bay Bridge north), bay grasses covered about 19,000 acres -- 80 percent of the 23,630-acre goal and an increase from about 15,500 acres in 2006.
- The massive grass bed on the Susquehanna Flats, which is now visible on satellite images, dominated this zone. Bay grasses in the Flats increased from 8,743 acres in 2006 to 11,726 acres in 2007, 97 percent of the restoration goal for that segment.
- Much of the rest of the upper Bay zone had little grasses, particularly on the Eastern Shore from the Sassafras River to the Chester River.
In the middle Bay zone (from the Chesapeake Bay Bridge to the Potomac River), bay grass acreage decreased slightly to about 30,000 acres -- 26 percent of the 115,229-acre restoration goal.
- Grass beds remained reasonably robust in the Severn, upper Patuxent and upper Potomac rivers.
- Bay grasses in the upper Potomac River increased from 4,234 acres in 2006 to 6,246 acres in 2007, exceeding Maryland and Virginia's restoration goals for that area.
- Grasses in the lower central Bay in Virginia decreased from 2,017 acres in 2006 to 1,342 acres in 2007.
- Unusually high salinities due to dry conditions during summer 2007 may have contributed to declines in the Chester and Magothy rivers and in Eastern Bay, where bay grass acreage fell from 565 acres in 2006 to 80 acres in 2007.
In the lower Bay zone (from the Potomac River south), researchers mapped about 16,000 acres of grasses -- an increase from a record low of 13,000 acres in 2006 and 35 percent of the 46,030-acre restoration goal.
- Many beds dominated by eelgrass, which dramatically died back during the hot summer of 2005, showed some modest recovery in 2007. For example, grass beds in the eastern lower Bay increased from 3,740 acres in 2006 to 5,134 acres in 2007 -- still far short of the 15,107-acre goal for this segment.
- Bay grasses continue to show a strong presence in many of the low-salinity and freshwater areas in the lower Bay zone, such as the Mattaponi, Pamunkey and Chickahominy rivers and creeks off the upper mainstem James River.
Over the past five to 10 years, scientists have witnessed large increases in bay grasses in many freshwater tributaries and segments of the Bay. But many middle- and high-salinity areas, such as Eastern Bay and Tangier Sound, are well below their peaks.
Annual bay grass acreage estimates are an indication of the Bay's response to pollution control efforts, such as implementation of agricultural best management practices (BMPs) and upgrades to wastewater treatment plants. Bay watershed residents can do their part to help bay grasses by reducing their use of lawn fertilizers, which contribute excess nutrients to local waterways and the Bay.
Bay grasses acreage is estimated through an aerial survey, which is flown from late spring to early fall. For additional information about the aerial survey and survey results, go to www.vims.edu/bio/sav/.