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Underwater Bay Grass Density

In 2014, there were an estimated 75,835 acres of underwater grasses in the Chesapeake Bay. High-density beds accounted for 62 percent of the total acreage, which is a two percent increase from 2013.

The densities of the grass beds growing in 2013 are as follows:

  • 62 percent of the beds had densities of 70 to 100 percent
  • 24 percent of the beds had densities of 40 to 70 percent
  • 10 percent of the beds had densities of 10 to 40 percent
  • Four percent of the beds had densities of less than 10 percent

May 05, 2011

Bay grasses, also known as submerged aquatic vegetation, are an integral part of the Chesapeake Bay ecosystem. Lee Karrh from the Maryland Department of Natural Resources (DNR) explains what bay grasses need to grow and why their survival is important to Bay critters.

May 05, 2011

What is submerged aquatic vegetation, and why is it important to the Chesapeake Bay?  Commonly known as “bay grasses” they among the most critical inhabitants of the Bay’s ecosystem.  Find out more about submerged aquatic vegetation, and see what people around Baltimore’s Belvedere Square had to say about it.


Restoring underwater grasses to the rivers, streams and shallow waters of the Chesapeake Bay will dramatically improve the Bay ecosystem. Grass beds provide food and shelter to fish, crustaceans and other species, add oxygen to the water, absorb nutrient pollution, reduce shoreline erosion and help suspended particles of sediment settle to the bottom.

Underwater grasses—also known as submerged aquatic vegetation or SAV—are sensitive to pollution but quick to respond to improvements in water quality. This means their abundance is a good indicator of Bay health. As pollution declines and water clarity improves, scientists expect underwater grass beds to expand.


In 2014, the Chesapeake Bay Program renewed its goal to achieve and sustain 185,000 acres of underwater grasses in the Chesapeake Bay. Progress toward this goal will be measured against a target of 90,000 acres by 2017 and 130,000 acres by 2025. 

Additional Information

Collecting data

This data is collected through an aerial survey flown from late spring to early fall by researchers with the Virginia Institute of Marine Science (VIMS). VIMS processes the photography in fall and winter and provides preliminary area totals the following spring. Visit the VIMS SAV website for more information about the survey or for segment-specific survey results.

Reporting data

The Chesapeake Bay Program reports underwater grass abundance on a Bay-wide and salinity zone scale. The latter method helps scientists find patterns in how underwater grasses are growing. To learn more, visit our Underwater Bay Grass Abundance (Baywide) or Underwater Bay Grass Abundance in Four Salinity Zones indicators.

Source of Data

Virginia Institute of Marine Science

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Annapolis, Maryland 21403
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