Monday, May 1, 2017

Underwater Grasses Help Restore the Bay

The underwater grass survey has been conducted in the Chesapeake Bay since 1984. That yearn just 38,229 acres of underwater grass were found. The 2016 underwater grass survey found 97,433 acres. This represented 53% of the Chesapeake Bay TMDL goal of 185,000 acres, and it exceeded an interim target of 90,000 acres set for 2017 under TMDL interim targets. The Bay’s 185,000-acre goal is based on actual acreages that could be observed in historical photographs of the Bay.

Restoring underwater grass beds is one of the goals of the nutrient and sediment reductions aimed at cleaning up the Bay, submerged grasses need sunlight to survive, and the clearer the water, the more sun they get. The grasses die as water is clouded by sediment and nutrient-fueled algae blooms. Underwater grass beds are a critical component of the Bay ecosystem. In addition to providing food for waterfowl and shelter for fish and crabs, they also pump oxygen into the water and trap sediments.

The recovery of the Chesapeake Bay’s underwater grasses has not been a straight line. Underwater grasses are impacted by storms and weather. The underwater grasses were knocked back to 48,195 acres by Hurricane Irene and Tropical Storm Lee in 2011, which sent a flood of nutrients and sediment into the Chesapeake.

Dry weather can also impact underwater grasses. Dry weather reduces the flow of nutrients and sediments into the Bay that can help the underwater grasses recover. However much of the recovery is in the moderate-salinity areas of the Mid Bay, a region dominated by widgeon grass, which is a notorious “boom and bust” species that can disappear as rapidly as it pops up. More than half of all underwater grasses in the Bay are found in that area.

Low flow, also increases the saltwater intrusion into the bay. Observations in some areas of the oligohaline (areas of moderate salinity) found a decline was in hydrilla, a nonnative species that is often quick to colonize but is also sensitive to higher salinities. Drier conditions (and therefore higher salinity) in some rivers might have caused localized diebacks. The very salty, polyhaline waters in the Lower Chesapeake Bay from the mouth of the Rappahannock and Tangier Island south, including the lower York and James rivers was observed to have only 14,226 acres of underwater grasses, which was a 15 % decrease.

Though this was a good year for underwater grasses, they are not yet robust and might not survive a large storm event. You and your group can help plant underwater grasses each year by participating in CBF's Grasses for the Masses program. During the winter months the Chesapeake Bay Foundation (CBF) conducts workshops where participants are given instructions and the tools necessary to grow the underwater grasses themselves. Then after about 12 weeks in the spring the groups can plant the grasses. Plantings are done at restoration sites during the months of April and May. Participants attend one of the grass plantings with CBF staff and other growers.

Planting underwater grass is an activity that requires a state permit. CBF maintains a permit for two planting sites and it is important that the grasses produced through the Grasses for the Masses program are planted only in these designated areas. In Northern Virginia the planting area is in Mason Neck State Park in Lorton. The 2017 Grasses for the Masses program was funded by the Chesapeake Bay Restoration Fund, using funds generated from the sale of Chesapeake Bay license plates. Most of the planting has been completed for the season. However, on June 5, 2017, in celebration of World Environment Day, the State Department with the help of the Chesapeake Bay Foundation will be planting their crop of underwater grasses at Mason Neck State Park in Lorton, Virginia.

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