Underwater bay grasses in Maryland are an important indicator of bay health, and the latest survey shows an increase in Maryland waters, Department of Natural Resources (DNR) Tidewater Ecosystem Assesment Director Robert Magnien has announced. Results released for the Chesapeake Bay show that last year Maryland bay grass acreage increased by an estimated 1,472 acres in 2000, an increase of 4% to 35,671 acres. Bay-wide acreage, including Virginia waters, increased by approximately 1% from 1999. Bay grasses in Maryland's Coastal Bays exhibited a slight, 6 percent decline to 9,696 acres in 2000.
"While we still have a long way to go in restoring the Chesapeake and Coastal Bays and their tributaries, the most recent findings show some positive trends," Dr. Magnien said. "Given the continued growth of Maryland's population, the work of the Tributary Teams and the Coastal Bays Program is critical to developing and implementing strategies to reduce excess nutrients and sediments."
These grasses are important because they provide food and habitat for a variety of creatures, including crabs, fish and waterfowl. Scientists have demonstrated that young blue crabs may be up to 30 times more abundant in Chesapeake Bay grass beds then in unvegetated areas. Bay grasses also protect shorelines from erosion by reducing wave action, helping to absorb nutrient pollutants, producing oxygen, and trapping sediments that cloud Bay waters. Overall, current bay grass acreage is only a small fraction of what existed historically, primarily due to effects of excessive nutrient and sediment pollution.
Increases in bay grasses primarily occurred in Maryland's upper and lower portions of the Chesapeake Bay as a result of improved water clarity from the low freshwater flows and runoff in 1999 and continued good water clarity in some areas in 2000. In the upper Bay, some of the most significant increases in bay grasses occurred in the Upper Eastern Shore, including the Elk, Sassafras and Bohemia rivers, and the upper portions of the Maryland mainstem and Susquehanna Flats. Along the Western Shore, significant increases were seen in the Gunpowder, Middle, and Bush rivers as well as Mattawoman and Piscataway creeks and the middle Potomac River. In the lower Bay, the Pocomoke Sound, Honga, Manokin and Big Annemessex rivers had significant increases. The Tangier Sound area continued the rebound that started in 1999 to record its highest coverge since 1993.
The largest declines in bay grass acreage were seen in the middle Bay area. On the Eastern Shore, Eastern Bay, the Little Choptank, Lower Chester and Lower Choptank rivers all suffered substantial declines. These declines was likely due in part to the severe mahogany tides experienced last Spring. This algae bloom is caused by excess nutrients and greatly reduces the amount of light reaching the underwater grasses. On the Western Shore, declines in bay grass coverage were evident in the South, Severn, Lower Potomac and Upper Patuxent rivers.
For only the second time since 1984, Maryland's Coastal Bays had a slight decline in bay grass acreage. While acreage declined approximately 6% from 1999 to 9,696 acres in 2000, overall Coastal Bays bay grass acreage has nearly doubled since 1984. The slight decrease in bay grass acreage may be due to the presence of macroalgae (large mats of algae that can smother bay grasses) and brown tide algae blooms in 2000. Currently DNR is conducting studies with other Coastal Bay scientists to examine the impact of macroalgae and other harmful algal blooms on bay grasses in the Coastal Bays ecosystem.
One of the bright spots in the 2000 survey is the large increase in bay grass acreage in the Gunpowder River. This area, which averaged 200 acres between 1990-1995, has steadily increased since 1996 up to 2,433 acres in 2000. The majority of the Gunpowder River's bay grasses are found in Dundee Creek. Lush beds of Wild Celery and Elodea carpet the bottom out to nearly eight feet in depth. Large numbers of fish are visible in crystal clear water. Not surprisingly, the area is surrounded by largely forested areas including Gunpowder State Park, Dundee-Saltpeter Park and Aberdeen
"The Bay grass beds in the Gunpowder River are of particular interest because this area held less than 100 acres in 1989. Now the area holds 24 times as much grass and is home to a great diversity of native species – both benefits of a forested watershed," said Dr. Magnien. "This area clearly shows the connections between watersheds, water quality and living resources, and is a model for conditions we'd like to see elsewhere."
Reduction of excess nutrients and sediments continue to be a focal point for Maryland's action plans for both the Chesapeake Bay and Coastal Bays. Two years ago, Governor Glendening signed the Coastal Bays Comprehensive Conservation Management Plan. This plan outlines a wide variety of actions to be taken for the restoration and protection of the Coastal Bays including bay grasses.
Along with the other Bay States, Maryland has renewed its goals to achieve a cleaner, healthier Chesapeake Bay through the Chesapeake 2000 agreement. In addition to requiring revised nutrient and sediment reduction goals, this agreement calls for protection and restoration of living resources, habitat and water quality. It specifically addresses the importance of bay grass by calling for a revision of restoration goals and the development and implementation of a strategy to accelerate restoration of bay grasses in areas of critical importance to the Bay's living resources.
Posted: 5-31-2001
