Underwater grasses in the Chesapeake Bay are coming back, but not nearly as quickly as needed to restore the polluted estuary.

An annual aerial survey of bay grasses by the federal-state Chesapeake Bay Program shows the bay and its tidal tributaries were covered by 65,000 acres of underwater grasses last year. That's an increase of ten percent from 2006.

However, the acreage is only about 35 percent of what Maryland, Virginia, Pennsylvania and the District of Columbia are aiming for by 2010.

The grasses are vital to restoring the Chesapeake because they filter excess nutrients from the water and provide habitat and food for fish and the bay's hallmark blue crabs.