The Chesapeake Bay Foundation has been planting stands of the grasses with some success, but cloudy brown water limits recovery. Most scientists think the bay would be a lot clearer if oyster stocks recovered. Oysters filter algae out of the water. Back in 1607, oysters were so numerous that they filtered the Chesapeake's entire water volume every three to four days. Now, at 1 percent historical levels, the oysters take a year or more to filter the Chesapeake.
Fewer oysters mean browner water and, thus, less sea grass and fewer crabs.
The disappearance of once-enormous oyster banks also eliminated habitat for many other creatures. Don Meritt, an oyster specialist at the University of Maryland's Horn Point Laboratory in Cambridge, Md., likens the huge vertical banks to coral reefs in tropical latitudes. Now, there aren't many of the banks left. All these factors may help to explain why blue crab populations have fallen by about 70 percent over the past 20 years. The Chesapeake at large is also receiving help.