The 2003 seagrass coverage in Maryland’s coastal bays increased by about 5 percent from 2002 to 2003 to approximately 11,069 acres according to the annual Virginia Institute of Marine Science report released last week. The 2003 acreage represents the second highest total documented in the Coastal Bays, and a 315 percent increase since the annual surveys began in 1986. The highest acreage coverage in the coastal bays was observed in 2001 (11,438 in MD).

The annual survey, conducted by aerial photography and on-site observations, documented increased coverage in the northern bays and slight losses in the southern bays. Grasses in Assawoman Bay increased 18 percent to 496 acres and Isle of Wight Bay increased 31 percent to 342 acres. Since there are only 835 acres of sea grass in Assawoman and Isle of Wight, the increased acreage provided substantial increases as a percentage. However, in the southern bays, Sinepuxent Bay had 117 fewer acres (6% decline) and Chincoteague Bay had 37 fewer acres (0.2% decline). Still about 90 percent of all coastal bays seagrasses are in the southern bays.

Bay grasses are important to the coastal bays because they provide habitat, food, and oxygen for a variety of bay organisms, including crabs, fish, and waterfowl. Bay grasses also help protect shorelines from erosion by reducing wave energy, help to absorb nutrients, and trap sediments that cloud bay waters.

Seagrass coverage is considered an indicator of the health of the bays and scientists are investigating ways to best use this information. The amount of coverage is being incorporated into a quantifiable goal for bay restoration. DNR personnel and researchers are looking at historical photos, sediment type and water depth to estimate potential coverage by grasses. One aspect of bay health will consist of how actual coverage meets potential coverage.

Since grasses provide habitat and food for a wide variety of organisms in the coastal bays most consider that “more is better”. Some, however, consider bay grasses to be a nuisance, especially as it dies and accumulates along shorelines in windrows. One should think of this as leaves falling in a forest, it’s a necessary part of the ecosystem as even the dead grasses provide food for many organisms that will eventually end up as food for fishes, crabs.

Water clarity is a very important factor that influences seagrass coverage. Sediment in the water column tends to decrease light penetration which is important to grasses. Also high amount of nutrients in the water column tend to promote growth of algae. Since algae are very small and can take up the nutrients faster than the rooted sea grasses, algae can become so abundant in the water that light is kept from reaching the grasses. Amount of rainfall can affect seagrass coverage. A very wet year would tend to wash sediment and nutrients into the bays which would tend to be detrimental to growth of grasses.

The highest seagrass cover was observed in 2001 which was considered a very dry year. The 2001 survey recorded a 10 percent increase in grass coverage. The following year, was considerably wetter and bay grass coverage decreased by 8 percent. Rainfall was slightly higher in 2003 than 2002 and still a slight increase in bay grass coverage was observed.