Chesapeake Bay Underwater Grasses Decline: Massive Storms to Blame

Underwater grasses in the Chesapeake Bay provide critical habitat and nursery grounds for fish and blue crabs. Yet scientists have recently announced that the grasses continued to decline last year, dropping by as much as 21 percent in 2011.

Sea grasses provide critical habitat for Bay animals. In addition, they serve as food for both turtles and birds. They can also absorb excess nutrients in the water, which helps keep the Chesapeake Bay clear, and they help reduce shoreline erosion by reducing wave action.

Massive storms in 2011, including Hurricane Irene and Tropical Storm Lee, dumped a torrent of mud and debris into the bay. This sediment stirred through the water and covered grasses, keeping them from the light that they needed to grow. The grasses were also stressed by excessively warm waters in 2010, and poor water quality since then has limited their exposure to sunlight.

In order to actually survey the grasses, a team conducted an aerial survey flown from late spring to early fall. The scientists charted the grasses by three "zones"--upper, middle and lower Bay--and into subsections by tributaries called "segments." In this way, they were able to get a birds-eye view of the sea grass while mathematically calculating the decline. In the end, the researchers found overall declines evident last year in all of the zones.

"It has been a rough few years for bay grasses, and we're not terribly surprised," said Bob Orth, a Virginia Institute of Marine Science researcher, who coordinated the survey of the sea grasses, in an interview with The Washington Post. "This year is going to be highly dependent on summertime temperatures."

It's not completely hopeless, though. There were two areas that showed notable resilience and expansion. Even so, how well the sea grass does will largely depend on future environmental conditions and storms.

Want to see the sea grass decline for yourself? Check out the new online mapping tool.