Nearly 200,000 acres of underwater bay grasses, also called submerged aquatic vegetation or SAV, are estimated to hav grown in the shallows and along the shorelines of the Chesapeake Bay and its rivers. By 1984, however, only 38,000 acres were documented from aerial surveys. Efforts to restore SAV have increased acreage over time but in 2003, a total of 64,709 acres of SAV were estimated to be growing in the Bay-a 30 percent decline from the previous year's tally. What causes SAV acreage to decline in the Bay and its rivers?

• The most important factor determining SAV growth and survival is light. Without it, SAV cannot perform photosynthesis and produce enough energy to grow.
• To determine how much light is reaching SAV leaves, scientists measure water clarity (or Secchi depth) and calculate the light attenuation coefficient. The higher the coefficient, the less light is reaching the plants' leaves.
• Water quality also affects the amount of light that reaches the leaves. Water quality is affected by:
  • Sediment, also called total suspended solids or TSS; sediment levels increase due to erosion from construction, forestry and agricultural practices.
  • Algae (measured as chlorophyll a) and epiphytes (microorganisms attached to the leaves).
  • Nutrients, including dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP).

Sediment levels increase due to erosion brought on by construction, forestry and agricultural practices. Nutrients, which in small quantities are beneficial (hence the name), in excess create enormous water quality problems. The overuse of fertilizers, runoff from livestock operations and outflow from sewage treatment facilities contribute to the Bay's high nutrient levels, which promote the excessive growth of algae in the water and on SAV leaves, blocking necessary light.

The Chesapeake Bay Program's Plan to Restore and Protect SAV

The Chesapeake Bay Program (CBP) has commited significant resources over the past 20 years to determine the causes for the decline and to identify the best methods for protecting and restoring SAV populations. In 2003, the CBP adopted a goal and strategy to accelerate SAV protection and restoration. The goal is to achieve 185,000 acres of SAV, baywide, by the year 2010. The strategy to achieve this goal is based on consensus among the formal and informal partners of the CBP, and its status will be reported annually and reevaluated in 2008.

More information on the types and functions of bay grasses.

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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.

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Last modified: 12/08/2004