Bay’s top underwater grass beds in VA, MD, PA, and DC

The Chesapeake Bay Foundation released a list of the top eight underwater grass beds in the Bay. CBF’s list of “hotbeds” includes two in Maryland, four in Virginia, one in Pennsylvania, and one in the Potomac River off of Washington, DC’s Roosevelt Island.

“Underwater Bay grasses provide some of the most productive and valuable habitat in the Bay,” said CBF underwater grass scientist Jill Bieri. “Because these beds help purify the water and serve as important habitat for fish and crabs and waterfowl, they are fascinating places to see wildlife. These hotbeds are ideal for recreational pursuits like fishing, birdwatching, kayaking, and, in some cases, even snorkeling.”

CBF’s hotbeds in Maryland are at Parsons Island (Eastern Bay, south of Kent Narrows) and Susquehanna Flats (southeast of Havre de Grace). In Virginia, the sites are at Poquoson Flats (at the mouth of the Poquoson River, southeast of Yorktown), New Point Comfort (at the mouth of Mobjack Bay), Fox Island (southwest of Crisfield, Maryland), and Shanks Island (south of Smith Island). The site near Roosevelt Island and Susquehanna River’s Nicks Island (north of Harrisburg Pennsylvania) in Pennsylvania round out the list.

“These hotbeds we selected represent tremendous diversity,” said Bieri. “The bed at Shanks Island is miles long, and with clear water and grasses growing six feet deep, provides a real glimpse of what the Bay must have looked like to John Smith in the early 1600s. The bed at Roosevelt Island—which has six species of grass, including a bed of wild celery that was planted by CBF and volunteers last year—provides a more modern lesson. Its location in the heart of an urban area demonstrates how resilient nature can be, but also reminds us that today’s conservation efforts have to coexist with development.”

Underwater grasses are indicators of good water quality because they generally are abundant only where water clarity is high. Today, underwater grasses cover only about 10 percent of their historic acreage in the Bay, primarily because of nutrient and sediment pollution. But scientists this year have noted strong grass growth in a number of areas, mostly in the lower Bay, which they attribute in part to 1999’s drought-reduced runoff.

“Real long-term improvements in underwater grass growth depend directly on efforts to reduce excess nutrients and sediments,” said Bieri. “We must protect remaining grass beds and improve water quality by reducing polluted runoff. This will help grasses spread naturally and enhance efforts to restore grasses where they historically grew.”

In the Chesapeake Bay and its tidal tributaries, 15 species of underwater grasses, representing nine plant families, commonly occur in waters less than six feet deep.

Note: Not all of the hotbed sites are open to every kind of recreation. Check laws and regulations regarding the sites before visiting.


Susquehanna Flats
Location: 39 32’N 76 02’W
South of Havre de Grace, MD
Salinity: Fresh
Species: Myriophyllum spicatum (Eurasian watermilfoil)
Hydrilla verticillata (hydrilla)
Vallisneria americana (wild celery)
Heteranthera dubia (water stargrass)
Ceratophyllum demersum (coontail)
Notes: Largest grass bed in Bay covering 6.5 square miles


Roosevelt Island
Location: 38 54’N 77 04’W
Potomac River, South of Georgetown
Salinity: Fresh
Species: Hydrilla verticillata (hydrilla)
Vallisneria americana (wild celery)
Heteranthera dubia (water stargrass)
Najas guadalupensis (southern naiad)
Najas minor (spiny naiad)
Zannichellia palustris (horned pondweed)
Notes: Unique urban setting with footpath that provides incredible view of remarkably clear water. Grasses growing six feet deep provide a glimpse of what the Bay was like historically and what it could be.

Parson Island
Location: 38 54’82”N 76 14’74”W
Eastern Bay, south of Kent Island
Salinity: Brackish
Species: Potamogetan pectinatus (sago pondweed)
Ruppia maritima (widgeon grass)
Salinity: Brackish (12 ppt)
Notes: Dense beds surrounding island, hotspot for fishing.


New Point Comfort
Location: 37 19’05”N 76 17’25”W
Mouth of Mobjack Bay, Matthews, VA
Salinity: Salt
Species: Zostera marina (eelgrass)
Ruppia maritima (widgeon grass)
Notes: Extensive beds surrounding island and along shoreline into Mobjack Bay.


Poquoson Flats
Location: 37 07’30”N 76 22’15”W
Adjacent to Plum Tree Island National Wildlife Refuge, VA
Salinity: Salt
Species: Zostera marina (eelgrass)
Ruppia maritima (widgeon grass)
Notes: Extensive bed over a mile wide and extending miles along shoreline, fishing hotspot.


Great Fox Island
Location: 37 54’30”N 75 52’30”W
Tangier Sound, South of Cedar Island Wildlife Management Area
Species: Zostera marina (eelgrass)
Ruppia maritima (widgeon grass)
Salinity: Salt
Notes: Extensive beds provide important food to diving ducks during their winter migration and critical shelter for juvenile blue crabs during the spring settlement.


Shanks Island
Location: 37 40’N 76 00’00”W
South of Smith Island, MD
Species: Zostera marina (eelgrass)
Ruppia maritima (widgeon grass)
Salinity: Salt
Notes: Bed over 2.5 miles long shows how extensive grass beds can be in Tangier Sound. As recently as the fifties, every island in Tangier Sound was flanked by underwater grass beds this size.


Nicks Island
Location: 40 ° 20’ N , 77 ° 1’ W
North of Harrisburg and just south of Duncannon
Species: Vallisneria americana (wild celery)
Heteranthera dubia (water stargrass)
Elodea canadensis (common waterweed)
Salinity: Fresh
Notes: Lush bed growing on the flowing Susquehanna River. Favorite spot for Smallmouth Bass and a diversity of other river species. Demonstrates the importance of underwater grasses in nontidal rivers as well as tidal waters.

Tips for Snorkeling in Underwater Grass Beds

Snorkeling in the Chesapeake Bay is different from doing it in the Caribbean or other tropical locations. Many more organisms grow in the water column, so the water is not as clear. In some areas of the bay, however, particularly around very thick, healthy grass beds, the water clear enough to allow snorkelers to see fish, turtles, and other marine organisms in their natural habitat. Many of our common fish, such as silversides, sunfish, yellow perch, and mumichugs, are spectacular when swimming.

Here are some tips for Chesapeake Bay snorkeling:


Pick a calm day that follows a few days without any storms or rain.
Move slowly so as not to disturb the fish or kick up sediments.
Keep your arms by your side and gently push off using just your feet. By leading with your eyes, you have a better chance to see the fish before they move away.
Edges are the best places to see fish; when you find a bare area within a grass bed, stop at the edge of the grass bed and wait to see what fish appear.
Caution: Please avoid disturbing grass beds when boating. Propellers and impellers may tear rooted vegetation out of bottom sediments. Also note that swimming in parts of the Bay and its tributaries may be restricted for all or part of the year. Check laws and regulations before going into the water.

Posted: 8-9-2000