What are bay grasses and why are they important? Lee Karrh of the Maryland Department of Natural Resources takes us on the Chesapeake Bay to see some submerged aquatic vegetation (SAV) firsthand in this Bay 101 video.
Produced by Matt Rath
Music: “A Moment of Jazz” by Ancelin
Underwater grasses provide significant benefits to aquatic life and serve many critical ecological functions in the Bay and its tributaries, such as:
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.
Note: 2012 acreage is based on preliminary data provided 3/28/13.
Long-term trend (1984-2012)
Short-term trend (2003-2012)
Change from previous year (2011-2012)*
*Note: The 2011 data previously reported changed due to the finalization of preliminary data.
**Note on Middle Bay acreage: 24,522 acres of underwater grasses (SAV) were mapped for 2012 and 29,023 acres were mapped in 2011. Portions of the Middle Bay zone, including the Middle, Upper and Western Branch of the Patuxent River; the Middle and Upper Potomac; Piscataway Creek; and the Anacostia River, representing 2,538 acres of SAV in 2012 (10% of the zone total) were not mapped in 2011. Comparing only the regions mapped in both 2011 and 2012, SAV decreased 24% from 28,749 acres in 2011 to 21,984 acres in 2012.
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.
Nita Sylvester
U.S. Environmental Protection Agency
(410) 267-5711
Virginia Institute of Marine Science
