In the shallow waters of the Chesapeake, Bay grasses sway in the aquatic breeze of the current. Bay grasses, also called submerged aquatic vegetation or SAV, are one the most important natural resources of the Chesapeake Bay. There are 16 common species of Bay grasses found in the Chesapeake Bay and tributaries.

Their presence or absence is an indicator of the health of a river or creek. Like all green plants, Bay grasses produce oxygen, a precious and sometimes decreasing commodity in the Chesapeake Bay.

Bay grasses also absorb nutrients like nitrogen and phosphorus. Excess nutrients in the Chesapeake Bay promote rapid algae growth known as blooms. Algal blooms reduce the amount of light reaching Bay grasses and when the blooms die and decompose, valuable oxygen is consumed.

In addition, Bay grasses filter and trap suspended sediment, which otherwise cloud the water and can bury bottom-dwelling organisms.

By reducing wave action, Bay grasses also help protect shorelines from erosion.

These plants are a key contributor to the energy cycling in the Bay. They provide food and habitat for invertebrates, fish and waterfowl. Microscopic zooplankton feed on decaying grasses and, in turn, become food for larger animals, such as fish and clams.

Barnacles and scallop larvae attach to the leaves and stems of eelgrass in the salty waters of the lower Bay.

Fish, like bluegill and largemouth bass, live in the freshwater grasses of the upper Bay. Immature blue crabs, minnows and juvenile fish, like striped bass, find protection from larger, hungrier mouths. Bay grasses are also a haven for vulnerable molting blue crabs, shielding them until their shells harden.

In the fall and winter, migrating waterfowl search the sediment for nutritious seeds, roots and tubers. Redhead grass and widgeon grass are favored foods of wigeon ducks, as well as many other waterfowl. Resident waterfowl may feed on different species of grasses year-round.

Bay grasses once formed immense underwater meadows, covering up to 200,000 acres in the Chesapeake Bay and its tributaries. With increasing development and nutrient pollution in the late 1960s and early 1970s, and Tropical Storm Agnes in 1972, the huge grass beds began to decline.

Factors that affect water clarity also affect the growth and survival of SAV. Suspended sediments and other solids cloud the water, reducing the amount of sunlight reaching the plants. Often, sediment covers the plants completely.

Sources of suspended sediment include runoff from farms, building sites and road construction. Shoreline erosion also adds sediment to the Bay.

Excess nutrients promote algae blooms that cloud the water, reducing sunlight, which the plants need to grow. Certain types of algae grow directly on the plants. Major sources of nutrients included sewage treatment plants, agricultural fields and fertilized lawns.

Bay grasses continued to disappear, hitting at all-time low of about 38,000 acres in 1984. Efforts to restore the water quality in the Chesapeake Bay watershed have had a positive effect on the grasses. In 2009, SAV distribution in the Bay was at 85,900 acres with increases occurring in the upper, middle and lower regions of the Chesapeake, marking only the second time such an increase has occurred since 2001.

Here are some actions the public can take to help the Chesapeake's underwater grasses:

  • Reduce the amount of fertilizers applied to lawns.
  • Replace some of a lawn's grass with native vegetation.
  • Make sure septic systems are properly maintained.
  • Plant strips of native vegetation along shorelines or streams to reduce erosion.
  • Divert runoff from paved surfaces to vegetated areas.
  • Avoid boating in shallow areas and Bay grass beds.
  • Pump boat waste to an onshore facility.