Seagrass
Underwater Grass Facts
- Underwater grasses, also called “seagrasses” or “Bay grasses”, are flowering vascular plants that grow in shallow water. They are often referred to as SAV (submerged aquatic vegetation).
- Sixteen (16) species of underwater grasses are commonly found in the shallow waters of coastal Virginia.
- Underwater grasses are a key contributor to energy cycling in coastal waters. Microscopic zooplankton feed on decaying grasses and, in turn, are food for larger organisms.
- Salinity is a primary factor affecting grass distribution. Grasses commonly found in areas of higher salinity include eelgrass (Zostera marina) and widgeon grass (Ruppia maritima). Grasses commonly found in areas of lower salinity include redhead grass (Potamogeton perfoliatus) and sago pondweed (Potamogeton pectinatus).
- Underwater grass distribution is influenced by temperature, light penetration, water depth, water currents and bottom sediment.
- Underwater grasses serve as a substrate and/or food for small species such as bay barnacles, sea squirts, sponges, Bay scallops, isopods, amphipods, snails and sea slugs. Grasses also provide a hiding place for small fish and crustaceans, such as pipefish, sticklebacks, anchovies, silversides, shrimp, blue crabs, clams and Lined seahorses, like Seacil!
No Blue Crabs?
Like the oyster fishery, the Blue Crab fishery is in a state of peril. Blue Crab numbers have declined dramatically in recent years.
...The Solution!
Underwater grass beds provide a safe haven for blue crabs as they shed their old shell (exoskeleton) and wait for their new shell to harden. An increase in grass beds will help increase the Blue Crab population!
Fewer Fish?
Underwater grass beds are a protective nursery for many juvenile fish including menhaden, herring, shad, spot, croaker, weakfish, red drum and silver perch.
...The Solution!
Give fish a chance, restore underwater grass beds!
Fewer Migrating Waterfowl?
Underwater grasses are a valuable food source for migrating waterfowl such as Brandt, the American Wigeon and Green-winged Teal. The Canvasback duck searches the sediment under grass beds for nutritious seeds, roots and tubers.
...Part of the Solution!
Feed the birds! Increase underwater grass beds!
Fun, Educational Materials
Seacil of the Seagrass
Official mascot of the Virginia Seaside Heritage Program, Seacil of the Seagrass is available as a costumed character and is featured as a cookie cutter with the message "Seacil the Seahorse Lives in the Seagrass! Support Seagrass Restoration!" Call while supplies last! (804) 698-4320 or e-mail: Virginia.Witmer@deq.virginia.gov.
"Build-A-Bed" Activity
Students help build a seagrass bed in small wading pools and populate the bed with some of the species that inhabit the seagrass bed. Engaging children in this activity helps teach them how seagrass is critical habitat to other marine species.
Download plans to construct and conduct this seagrass educational activity - Build-A-Bed Activity Design and Instructions - pdf
Links to SAV Websites/On-Line Articles
Virginia Institute of Marine Science - www.vims.edu/bio/sav/
VIMS SAV Restoration Page - www.vims.edu/bio/sav/restoration/
Chesapeake Bay Program (EPA)- www.chesapeakebay.net/baygras.htm
"About Bay Grasses" - Alliance for the Chesapeake Bay "Bay Journal", September 2006 -
Restoration of eelgrass (zostera marina) beds is a main component of the Virginia Seaside Heritage Program, a public-private effort focusing on the restoration of aquatic resources and sustainable industries on the seaside of Virginia’s Eastern Shore.
Underwater Grass Beds provide habitat!
Grass beds provide food and habitat for waterfowl, fish, shellfish and invertebrates. Underwater grasses, such as 
eelgrass, create a special habitat for many aquatic organisms and a pivotal role in the life of many aquatic species, including the Bay scallop and the Lined seahorse. Restored grass beds on the seaside could signal the return of many of these species.
Underwater Grasses Produce Oxygen!
Grasses produce oxygen in the water column as part of the photosynthetic process.
Underwater grass Beds control sediment!
Grass beds filter and trap sediment that can cloud the water and bury bottom-dwelling organisms, such as oysters.
Underwater Grass beds protect shorelines!
Grass beds protect shorelines from erosion by absorbing wave energy.
Underwater Grasses remove excess nutrients!
Grasses remove excess nutrients, such as nitrogen and phosphorus, that could fuel unwanted growth of algae in surrounding waters. Grasses require these nutrients for growth and reproduction.
What is causing declines in underwater grasses?
Underwater grass growth and survival depends upon the amount of light that reaches the plants.
When the amount of light is too low, the plants can no longer photosynthesize and produce enough food and energy to grow.
High sediment levels resulting from land erosion blocks some of the light that grasses need to survive and grow.
High nutrient levels, caused by the excessive use of fertilizers, runoff and sewage outflow indirectly affect grasses by allowing excessive algae to grow both in the water and on the grass blades, further blocking the necessary light.
Boat propellers and impellers have torn rooted vegetation out of bottom sediments and dredging has caused severe scarring of underwater grass beds.
Seed Broadcasting: A seagrass restoration technique reaping great rewards on Virginia’s Seaside
Underwater grass restoration on the seaside focuses on the redistribution of grass seeds. Seeds are sustainably harvested from productive grass beds and transplanted to areas in need of restoration.
Aerial photos, like the one above, show the phenomenal success of eelgrass plots restored on Virginia’s seaside using the seed broadcasting technique. This plot in the shape of a “W” restored in 2000 is thriving and spreading naturally to the surrounding area!
Learn more about restoration of seagrass on Virginia's Eastern Shore by the Virginia CZM Program ! Visit the Virginia Seaside Heritage Program page!
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This web site is provided by the Virginia Coastal Zone Management Program through a Coastal Zone Management Act grant from the National Oceanic and Atmospheric Administration, US Department of Commerce.