According to preliminary data from the Virginia Institute of Marine Science (VIMS), an estimated 104,843 acres of underwater grasses were observed in the Chesapeake Bay in 2017: 14,843 acres greater than the Chesapeake Bay Program’s 2017 restoration target and 57 percent of the partnership’s 185,000-acre goal.
Submerged Aquatic Vegetation (SAV) Abundance (1984-2017)
Submerged Aquatic Vegetation (SAV) Abundance (2010-2017)
For the third year in a row, underwater grass abundance in the Chesapeake Bay has reached the highest amount ever recorded by VIMS. For the first time in our decades-long history of monitoring submerged aquatic vegetation, total abundance has surpassed 100,000 acres. This total is about half of the acreage we believe existed here in the early twentieth century.
Experts attribute the rise in underwater grasses to increases in the tidal fresh, moderately salty and very salty regions of the Bay, and reported the following totals in the Bay’s four salinity zones:
- An estimated 19,880 acres of underwater grasses were observed in the tidal fresh salinity zone: a 96 percent achievement of the region’s 20,602-acre goal.
- An estimated 8,398 acres of underwater grasses were observed in the slightly salty or oligohaline salinity zone: an 81 percent achievement of the region’s 10,334-acre goal.
- An estimated 61,331 acres of underwater grasses were observed in the moderately salty or mesohaline salinity zone: a 51 percent achievement of the region’s 120,306-acre goal.
- An estimated 15,234 acres of underwater grasses were observed in the very salty or polyhaline salinity zone: a 45 percent achievement of the region’s 33,647-acre goal.
The very salty portion of the Bay saw a sustained recovery of eelgrass, while the moderately salty portion of the Bay saw a continued increase in widgeon grass. Because widgeon grass is a “boom and bust” species whose abundance can rise and fall from year to year, a widgeon-dominant spike is not guaranteed to persist in future seasons. The wild celery, water stargrass and other species that have returned and reached new parts of the tidal fresh portion of the Bay are less susceptible to such fluctuations in abundance.
Underwater grasses are sensitive to pollution but quick to respond to improvements in water quality. Before Europeans colonized the region, up to 600,000 acres of underwater grasses grew 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 underwater grass recovery.
Because grass beds provide food and shelter to fish and wildlife, sequester carbon, add oxygen to the water, absorb nutrient pollution, reduce shoreline erosion and help suspended particles of sediment settle to the bottom, their restoration will dramatically improve the Bay ecosystem. Indeed, the value of the carbon sequestration, nitrogen removal and wildlife habitat provided by the 97,000 acres of grasses that grew here in 2016 reached an estimated $220 million.
More information about underwater grass abundance in the Chesapeake Bay can be found in a report from the Virginia Institute of Marine Science (VIMS).