Bay Grasses - SAV - general info

Which of the following isn't a naturally occuring Bay grass?

	eelgrass
	widgeon grass
	redhead grass
	hydrilla

Underwater Bay Grasses

Underwater bay grasses, also called submerged aquatic vegetation or SAV, once grew in abundance-covering an estimated 200,000 acres-along the shallows and shorelines of the Chesapeake Bay. SAV provides protection and nursery habitat for a broad range of aquatic organisms, contribute to the oxygenation of the water and prevent erosion and sedimentation.

In 2003 a total of only 64,709 acres of grasses were estimated to be present in the Bay-which represents a 30 percent decline from the previous year's tally. This decline is both natural and man-made, and creates concern for the health of the resource, which provides sustenance and shelter to many other species.

Learn about restoration of Chesapeake Bay Grasses

SAV as Important Bay Habitat

Underwater bay grasses provide crucial habitat for a host of aquatic organisms, including fish, shellfish, invertebrates and waterfowl. These important plant communities are key contributors to the energy cycling in the Bay. Here are some components to the process:

The blade surface of SAV serves as substrate for microscopic algae and protozoa, known as epiphytes, which minnows graze on;
Zooplankton feed on decaying SAV particles and provide food for larger organisms;
Bay barnacles, sea squirts, sponges, isopods, amphipods, snails and sea slugs also use SAV leaves as substrate and food;
Crustaceans and juvenile fish seek cover from larger predators among SAV leaves; and
Migrating waterfowl, such as the American wigeon, green-winged teal and canvasback duck, forage along the base of SAV plants for seeds, roots and tubers, while resident waterfowl feed year-round on SAV.

Learn more see the conceptual model of SAV habitat interactions.

SAV Anatomy

The roots, stems and leaves of SAV contain similar conducting tissues characteristic of terrestrial vascular plants, but they are adapted to enable them to survive in an aquatic environment.

SAV leaves and stems lack the waxy 'cuticle' present in most terrestrial plants. Gases and nutrients can thus be exchanged between the plant and surrounding water.
SAV leaves and stems also contain specialized, air-filled cells, called 'aerenchyma,' which provide the plants with additional bouyancy and support.

SAV Function

Bay grasses support the Bay's health by:

Generating food and habitat for waterfowl, fish, shellfish and invertebrates;
Adding oxygen to the water column during photsynthesis;
Filtering and trapping sediment that otherwise would bury benthic organisms and cloud the water column;
Inhibiting wave action that erodes shorelines; and
Absorbing excess nutrients (which they require for growth), such as nitrogen and phosphorus, that may fuel the growth of unwanted algae in surrounding waters.

Types of Underwater Bay Grasses

Submerged Aquatic Vegetation Sixteen species of SAV can be found in the shallows of the Bay and its tributaries. Their distribution depends on each species' habitat requirements. Salinity is the primary factor affecting their distribution, thus SAV species are generally categorized according to their salinity tolerance.

Tidal-fresh species require salinity levels of between 0 and 0.5 parts per thousand.
Oligohaline (slightly brackish) species require 0.5 to 5 ppt.
Mesohaline (moderately brackish) species require 5 to 18 ppt.
Polyhaline (high salinity) species require 18 to 30 ppt.

Eelgrass (Zostera marina) and widgeon grass (Ruppia maritima) are most commonly found in high salinity areas; redhead grass (Potamogeton perfoliatus) and sago pondweed (Potamogeton pectinatus) occur in low salinity areas.

Common underwater Bay grasses

How YOU can help:

Always use pumpout stations to dispose of boat waste.
Avoid vegetated shallows when planning dredging or pier construction.
Participate in citizen water quality monitoring.
Help environmental organizations plant Bay grasses.
Be a responsible boater and avoid disturbing Bay grass beds. Propellers and impellers may tear rooted vegetation out of bottom sediments.
Use environmentally friendly landscaping techniques that require less fertilizer, prevent erosion, and utilize native plants. This helps prevent sediments and nutrients from reaching Bay waters.
Use your car and other gasoline engines less. Their exhaust contains nitrous oxides which pollute Chesapeake Bay and its rivers.

Other Sites of Interest:

To bookmark this page, please use this URL: http://www.chesapeakebay.net/baygras.htm

For more information, contact the Chesapeake Bay Program Office:
410 Severn Avenue, Suite 109, Annapolis, MD 21403 / Tel: (800) YOUR-BAY / Fax: (410) 267-5777.