No matter what they're called—underwater grasses, baygrasses, or submerged aquatic vegetation (SAV)—underwater flowering plants play a key role in the health of the Chesapeake Bay and coastal waters worldwide.
Researchers at the Virginia Institute of Marine Science have monitored the Bay's changing SAV coverage since 1978, conduct research on SAV ecology, and pioneered methods to restore eelgrass to Virginia's seaside lagoons—the world's most successful seagrass restoration project.
Today, VIMS, the Chesapeake Bay Program, and a host of other state and federal partners monitor and restore underwater grasses to ensure they continue to benefit marine life and coastal communities.
About Underwater Grasses
Benefits of Underwater Grasses
The Chesapeake Bay is home to 26 different species of submersed aquatic vegetation, including freshwater plants like wild celery, estuarine plants like sago pondweed and redhead grass, and marine species like eelgrass and widgeon grass. The specific habitat needs differ among plant species, with the most important factor being salinity. Moving from the fresher to saltier parts of the Bay there are predictable changes in the identity of the dominant underwater grasses.
Beds of underwater grasses are a nursery habitat, providing food and refuge for blue crabs, young striped bass, bay scallops, waterfowl, and many other aquatic species.
Underwater grasses take up nutrients, reduce shoreline erosion, trap particles, stabilize sediments, and add oxygen to the water.
Underwater grasses serve as a "canary in the coalmine" that scientists can use to gauge the health of the Chesapeake Bay.
Healthy beds of underwater grasses benefit people in Virginia and around the globe, from watermen and seafood lovers to recreational anglers, beachgoers, boaters, and waterfront residents.
How will climate change and nutrient management affect the future of Chesapeake Bay seagrasses and aquatic plants?
Threats to Underwater Grasses
A number of stressors affect underwater grasses, but not all grasses are affected the same way. The negative impacts of each of the threats listed below differs among the species.
Threats to Underwater Grasses
Underwater grasses are vascular, rooted, flowering plants that require high levels of sunlight for photosynthesis and growth. Runoff of sediment due to deforestation, urban sprawl, and other watershed disturbances has significantly increased the turbidity of coastal waters, blocking needed sunlight. Turbid conditions restrict grasses to shallow waters or cause them to die back entirely. In general, the freshwater species are more tolerant of low-light conditions.
Farms, yards, wastewater treatment plants, and car exhaust are all sources of excess nitrogen to coastal waters. This nutrient pollution can fuel phytoplankton blooms in the water that shade underlying grass beds; and fuel algal blocking light by growing directly on SAV leaves.
Though education and regulation have decreased the threat, boat propellers and fishing gear continue to destroy underwater grasses by cutting shoots and uprooting plants.
Eelgrasses prefer cool water and Chesapeake Bay is at the southern edge of their range. As summer water temperatures continue to climb, eelgrasses may not survive the heat. Drastic eelgrass diebacks following the very hot summers of 2005 and 2011 may portend the future fate of this important species in the lower Chesapeake Bay.
Eelgrass Restoration
Eelgrass Restoration
VIMS researchers helped pioneer the equipment and methods used to restore eelgrass not only in Virginia but worldwide. Their work has led to advancements in tools and techniques for gathering, preserving, and deploying both shoots and seeds. Learn more.
Efforts to restore eelgrass in the Chesapeake Bay by transplanting have failed to significantly increase its overall abundance in most locations. Early success in restoring eelgrass to the lower York and James rivers via seed has also not persisted in the long run. Poor water quality and increasing water temperatures are likely responsible. Current restoration efforts in the Bay focus on the Poquoson Flats.
VIMS' success in restoring eelgrass to the cool, clear waters of Virginia's seaside bays has led to interest from scientists and resource managers in both northern Europe and Australia.
At its most pristine, Chesapeake Bay may have supported more than 600,000 acres of underwater grasses. Today, Bay coverage is below 100,000 acres. Globally, seagrasses have declined almost 30% since the late 1800s, and a football field worth of seagrass now disappears every second.
