Report: Underwater grasses resurge in the Chesapeake Bay

The abundance of underwater grasses throughout the Chesapeake Bay resurged by 24 percent between 2012 and 2013, reversing a three-year decline, the Chesapeake Bay Program said this week.

Scientists credit better water quality for the "modest" recovery of eelgrass in the bay's shallow, salty waters and the "rapid expansion" of widgeongrass in the mid-bay. The health of underwater grasses is considered a barometer for overall bay health.

"These bay grasses are the canary in the cage, and an indication of water quality and of the efforts to improve water quality," Robert Orth of the Virginia Institute of Marine Science said when he helped release the new numbers.

VIMS, in Gloucester Point, has worked for years to restore eelgrass to the bay, seeing great success seeding the tidal bays of the Eastern Shore. The institute is affiliated with the College of William and Mary in Williamsburg and with CPB a regional partnership of federal, state and local agencies, academic institutions and environmental and nonprofit groups. The partnership is tasked with protecting and restoring the bay, which deteriorated for decades from pollution and nutrient overload from stormwater runoff.

Every year from late spring to early fall, grass beds in the bay are tracked using aerial surveys. While the data is still gathered the same way, this year the grasses were mapped according to salinity zones rather than geographic zones to better reflect different species and how they respond to environmental stressors, explained Lee Karrh, a biologist with the Maryland Department of Natural Resources. The waters of the bay range from no salinity to sea-water strength salinity.

The latest surveys show an uptick in grass beds from 48,195 acres to 59,927 acres, or about a third of the ultimate goal of 185,000 acres. Orth said most of that increase came from a boom in widgeongrass in the mid-bay

The CBP also updated decades of its past surveys to correlate with the new salinity zone map, Karrh said. Between 1984 and 2013, the data show:

Tidal Fresh Salinity Zone: In the no-salt waters of the bay, grass abundance ranged from a low of 6,900 acres (1995) to a high of 25,481 acres (2008), averaging 12,399 acres. From 2012 to 2013, the zone's grass beds increased by 1,841 acres to 13,990 acres.

Oligohaline Salinity Zone: In the bay's slightly salty waters, abundance ranged from 653 acres (1984) to 13,918 acres (2005), averaging 6,680 acres. Between 2012 and 2013, grasses increased by 78 acres to 5,590 acres.

Mesohaline Salinity Zone: In the bay's moderately salty waters, grass beds ranged from 15,636 acres (1984) to 48,443 acres (2005), averaging 27,851 acres. From 2012 to 2013, they increased 5,598 acres to 25,579 acres.

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Report: Underwater grasses resurge in the Chesapeake Bay