According to preliminary data from the Virginia Institute of Marine Science (VIMS), 62,169 acres of underwater grasses were mapped in the Chesapeake Bay in 2020. This is 48% of the Chesapeake Bay Program’s 2025 restoration target of 130,000 acres and 34% of the partnership’s 185,000-acre goal.
Although the 62,169 acres mapped in 2020 is a 60% increase from the 38,958 acres observed during the first survey in 1984, it is a 20% decrease from the current 10-year average of 78,168 acres and a 7% decrease from 2019 when 66,684 acres of underwater grasses were mapped.
Experts attribute the decline in underwater grasses to decreases in the moderately salty and slightly salty regions of the Bay, and reported the following totals in the Bay’s four salinity zones:
- Tidal Fresh Zone: Underwater grass beds increased from 17,618 acres to 18,478 acres, a 90% achievement of the region’s 20,602-acre goal.
- Oligohaline Zone (slightly salty): Underwater grass beds decreased from 9,029 acres to 8,086 acres, a 78% achievement of the region’s 10,334-acre goal.
- Mesohaline Zone (moderately salty): Underwater grass beds decreased from 28,061 acres to 22,377 acres, a 19% achievement of the region’s 120,306-acre goal.
- Polyhaline Zone (very salty): Underwater grass beds increased from 11,975 acres to 13,228 acres, 39% achievement of the region’s 33,647-acre goal.
In 2020, the largest declines in terms of total area (-5,684 acres) were observed in the mesohaline zone, including continued loss in the Tangier South area and new large decreases in Eastern Bay, the mouth of the Choptank River, and in the Little Choptank River. Experts attribute the losses largely to a decline in widgeon grass. Widgeon grass is a species whose abundance can rise and fall from year to year in response to changes in water quality. For example, in 2018, widgeon grass increased in the mesohaline and northern polyhaline salinity zones, but subsequently declined in 2019 which mirrors a similar rapid increase in 2001 and 2002 that was followed by about a 50% decline in 2003.
Underwater grass beds are critical to the Chesapeake Bay ecosystem. They provide food and shelter to fish and wildlife, sequester carbon and buffer PH, add oxygen to the water, absorb nutrient pollution, reduce shoreline erosion and help suspended particles of sediment settle to the bottom. Because they are sensitive to pollution but quick to respond to improvements in water quality, underwater grass abundance is a good indicator of the Bay’s health. Before Europeans colonized the region, up to 600,000 acres of underwater grasses may have grown along the shorelines of the Bay and its tributaries. By the mid-1980s, nutrient and sediment pollution had weakened or eliminated many of these grass beds. While climate change, shoreline hardening and stressors that reduce water clarity will continue to impact our restoration success, many of these stressors can be managed with on-the-ground efforts to reduce pollution and research has shown that nutrient reductions made under the Chesapeake Bay Total Maximum Daily Load (Bay TMDL) have played a critical role in the overall underwater grass recovery documented since the Bay-wide aerial survey began in 1984.
More information about underwater grass abundance in the Chesapeake Bay can be found on the Virginia Institute of Marine Science (VIMS) website.
To achieve this outcome, Chesapeake Bay Program partners have committed to:
- Supporting efforts to conserve and restore current and future underwater grass habitat and habitat conditions in the Chesapeake Bay;
- Protecting existing and recovering underwater grasses in the Chesapeake Bay;
- Restoring underwater grasses in the Chesapeake Bay;
- Enhancing underwater grass research and monitoring in the Chesapeake Bay watershed; and
- Enhancing citizen involvement, public education and outreach in the watershed.
Monitoring and assessing progress toward the outcome will occur through data related to underwater grass distribution and abundance.
As part of the Chesapeake Bay Program’s partnership-wide implementation of adaptive management, progress toward this outcome was reviewed and discussed by the Management Board in November of 2019.
Logic & Action Plan
Chesapeake Bay Program partners have committed to taking a series of specific actions that will support the management approaches listed above.
The Submerged Aquatic Vegetation Workgroup, which is part of the Vital Habitats Goal Implementation Team leads the effort to achieve this outcome. It works in partnership with the Sustainable Fisheries and Water Quality goal implementation teams.
Participating partners include:
- Maryland Department of Natural Resources (State of Maryland)
- Maryland Department of the Environment (State of Maryland)
- University of Maryland Center for Environmental Science (State of Maryland)
- St. Mary’s College of Maryland
- Virginia Institute of Marine Science (Commonwealth of Virginia)
- Virginia Department of the Environmental Quality (State of Virginia)
- Virginia Marine Resources Commission
- Virginia Coastal Zone Management Program
- Old Dominion University
- Department of Energy and Environment (District of Columbia)
- National Oceanic and Atmospheric Administration
- U.S. Army Corps of Engineers
- U.S. Environmental Protection Agency
- U.S. Fish and Wildlife Service
- U.S. Geological Survey
- Smithsonian Environmental Research Center
- Chesapeake Bay Foundation
- Local Riverkeeper and Watershed Organizations