Underwater grasses in the Chesapeake Bay, a key indicator of the health of the waterway, decreased last year with high water temperatures and poor water quality eyed as factors, researchers said Thursday as they released the results of an annual survey.
The aerial survey conducted by the Virginia Institute of Marine Science found the acres covered by the grasses last year dropped 7 percent from the year before, but the researchers say the acreage is still at its third highest level since annual surveys began in 1984.
Bay grasses are a key indicator of bay health because they provide food and habitat for many species, as well as helping water quality by adding oxygen and trapping sediment.
The upper bay and the upper Potomac River had the most coverage, particularly in the Susquehanna Flats in the upper bay. However, coverage in the upper bay slipped to 90 percent of the restoration goal after reaching 100 percent the year before.
Large increases were seen in the Chesapeake and Delaware Canal and part of the Sassafras River, but they were offset in part by losses elsewhere.
In the mid-bay, acreage dropped 11 percent to 31 percent of the restoration goal while in the lower bay coverage increased 1 percent to almost half of the restoration goal. However, researchers said some of that increase was due to a non-native species, which accounts for almost all of the grasses in some Virginia rivers.
Much of the gains also were in shallow areas where light is not blocked by sediment and algae blooms, with grasses nonexistent or struggling in many deeper areas. Most of the lower-bay gains were in the Upper Rappahannock, lower Piankatank, the mouth of the James and the upper James Rivers, offsetting losses in other areas, the researchers said.
Bob Orth, scientist with the Virginia Institute of Marine Science and leader of the bay-wide annual survey, said last year was one of the hottest on record for bay water temperatures, and high water temperatures along with water quality hurt bay grasses, particularly a type known as eel grass.
“Some parts of the bay literally got cooked in June,” Orth said.
The survey results were released by the Chesapeake Bay Program, a joint state and federal effort that has led bay restoration efforts.
Will Baker, president of the Chesapeake Bay Foundation, said the results showed the need for the much-criticized “pollution diet” being implemented by the federal Environmental Protection Agency. The EPA has taken the lead in the decades-long bay restoration effort in response to a presidential order, but the stricter approach has spawned opposition from agricultural and business interests.
“This is a clear indication that pollution must be reduced further and the ‘pollution diet’ for the bay is the right strategy going forward,” said Baker.
The foundation sued the EPA over the slow pace of restoration efforts.
“What we’re hearing so much these days is that the bay is getting better, so we don’t need to put the controls in place to reduce pollution further, obviously these data dispute that,'” Baker said.
VIMS grass survey — www.vims.edu/bio/sav
Chesapeake Bay Program bay grass site — www.chesapeakebay.net/status_baygrasses.aspx