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Underwater Bay Grass Density

In 2013, high density beds accounted for 60 percent of the total acreage, which is 12 percent higher than 2012.

The density classifications for the beds in 2013 are as follows:

  • 60% of the beds had densities of 70-100%
  • 19% of the beds had densities of 40-70%
  • 13% of the beds had densities of 10-40%%
  • 8% of the beds had densities of <10%

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.

Produced by Matt Rath
Music: “A Moment of Jazz” by Ancelin

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.

Produced by Matt Rath
Music: “Neapolitan song” by Astrid & Ruediger Kramer
“2 percenter” by Williamson
“All of Me” by Double F


Underwater grasses provide significant benefits to aquatic life and serve many critical ecological functions in the Bay and its tributaries, such as:

  • Providing shelter for young striped bass, blue crabs and other species
  • Improving water clarity by helping suspended sediment particles settle to the bottom
  • Adding oxygen to the water
  • Reducing shoreline erosion

Scientists believe that having more grasses in the Bay and rivers will dramatically improve the entire ecosystem. The expectation is that as nutrient and sediment pollution decrease and water clarity improves, underwater grass acreages should expand. Experts closely monitor underwater grasses because their well-being is dependent on good local water quality.  Therefore, their abundance is an excellent measure of the Bay’s health..


The goal is to have 185,000 acres of underwater grasses in the Chesapeake Bay. This acreage represents approximate historic abundance from the 1930s to present.

Additional Information

Changes to Goals Expected in 2014

The CBP SAV workgroup is in the process of recommending changes to the segment-specific goals to align them with water quality standards adopted by Bay jurisdictions.  This will result in revisions to the 185,000-acres baywide goal.

Historic Bay Grass Data

Review of photographs from a number of sites dating back to 1937 suggests that close to 200,000 acres of bay grasses – also called submerged aquatic vegetation or SAV – may have once grown along the Bay’s shorelines.  However, by 1984, bay grass acreage had fallen to a low of about 38,000 acres. More nutrient and sediment pollution in the water has choked or eliminated bay grasses in many areas, contributing to declines in SAV acreage throughout the Bay.

Collecting Bay Grass Abundance Data

The aerial SAV survey is flown from late spring to early fall. The photography is processed in the fall and winter, and preliminary area totals are usually available the following spring.  Visit the Virginia Institute of Marine Science website for additional information about the aerial survey and for segment-specific survey results.

Setting Bay-wide Goals for Bay Grass Restoration

In 1993, the Bay Program agreed to work to restore bay grasses to historic levels. It set an interim restoration goal of 114,000 acres – the total area vegetated at one time or another since the early 1970s. Based on recovery rates at that time, the goal was expected to be achieved by 2005.

In the Chesapeake 2000 agreement, the Bay Program recommitted to the existing goal of protecting and restoring 114,000 acres of bay grasses.  They also agreed to “revise SAV restoration goals and strategies to reflect historic abundance, measured as acreage and density from the 1930s to the present.”

In 2003, the Bay Program adopted the Strategy to Accelerate the Protection and Restoration of Submerged Aquatic Vegetation in the Chesapeake Bay. The strategy included a new Bay-wide restoration goal of 185,000 acres by 2010. This acreage represents approximate historic abundance from the 1930s to present.

Scientists believe that having more bay grasses in the Bay will dramatically improve the entire ecosystem. As nutrient and sediment pollution decreases and water clarity improves, bay grass acreage should expand.

Source of Data

Virginia Institute of Marine Science

410 Severn Avenue / Suite 112
Annapolis, Maryland 21403
Tel: (800) YOUR-BAY / Fax: (410) 267-5777
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