Underwater grasses across the Chesapeake Bay reached their highest acreage since 2018 last year, according to the annual survey released this week — but the news was decidedly mixed for Southern Maryland’s two major rivers, with the Patuxent posting some of the Bay’s sharpest gains while the Potomac was singled out as one of its more troubling declines.
The Bay-wide total reached 89,385 acres of submerged aquatic vegetation (SAV) in 2025, up 7% from 83,252 acres in 2024 and the sixth-highest total recorded since the Virginia Institute of Marine Science (VIMS) began the annual survey in 1984. That history offers useful perspective: the Bay’s SAV coverage started at just 38,958 acres in 1984, peaked at 108,078 acres in 2018, and has averaged 70,978 acres over the life of the survey — meaning 2025’s total sits well above the long-term norm even though it remains far from the ultimate goal. That goal, set under the Chesapeake Bay Watershed Agreement, was raised this year to 196,600 acres, and the Bay’s current total represents just 45% of it. In the nearer term, the Bay came within 615 acres of a 2030 interim milestone of 90,000 acres.
In Maryland’s portion of the Bay specifically, grass coverage jumped nearly 13%, from 36,799 acres in 2024 to 41,419 acres in 2025 — about 36% of the state’s own 114,065-acre restoration target.
A tale of two Southern Maryland rivers
The Lower Patuxent River, which runs along the Calvert County shoreline, was one of the standout local success stories: SAV there expanded from 17 to 52 acres, a 201% increase, part of a broader pattern of 50%-or-greater gains across several rivers on both the Eastern and western shores. The Potomac River told a very different story. The Chesapeake Bay Foundation specifically named the Potomac, alongside the Patapsco and Gunpowder rivers, among the waterways experiencing what the group called “troubling declines,” attributing the losses to polluted runoff and increasingly intense rainstorms. In Charles County, Mattawoman Creek — a Potomac tributary — lost 200 acres of grass even while still holding onto 85% of its 792-acre restoration goal.
“More underwater grass means more habitat for blue crabs and fish, cleaner water, and a more resilient Chesapeake Bay,” said Maryland Department of Natural Resources Secretary Josh Kurtz. “This year’s increase is welcome progress, but it also reinforces the work ahead. We need to keep reducing pollution, protecting existing underwater grass beds, and restoring the shallow-water habitats that allow these plants and the Bay life that depends on them to thrive.”
Freshwater rivers rebound
Maryland’s freshwater and low-salinity rivers gained a combined 1,059 acres, and seven river segments met or exceeded their restoration goals outright: Northern Chesapeake Bay segment 1 (102% of a 754-acre goal), the North East River (179%), the Upper Chester River (531%), the Upper Sassafras River (275%), the Bush River (158%), the Upper Gunpowder River (107%), and the Back River, which reached 712% of its modest 30-acre target. Two more segments came close — Northern Chesapeake Bay segment 2, which includes the sprawling Susquehanna Flats, reached 91% of its 12,149-acre goal. Freshwater areas of the Bay support an especially diverse SAV community, including wild celery, water stargrass, several species of naiads, and pondweeds — a mix scientists say makes these beds more resilient and better able to bounce back from disturbance than single-species stands.
Mid-Bay and Eastern Shore gains
The moderately salty mid-Bay saw some of the largest raw gains, growing from 20,729 to 24,289 acres — about 17% — even though no individual mid-Bay segment reached its restoration goal outright. Those gains were driven largely by widgeon grass and sago pondweed, species that can expand quickly when conditions align but decline just as fast when they don’t. “These communities are dynamic: when light, salinity and other growing conditions align, species such as widgeon grass can spread quickly,” said Brooke Landry, SAV program chief for Maryland DNR and chair of the Chesapeake Bay Program’s SAV Workgroup. “The flip side is that the same beds can decline just as quickly when conditions deteriorate, which is why long-term monitoring, sustained water-quality improvements, and protection of existing habitat remain so important.”
Eight Eastern Shore rivers or river segments grew by 50% or more. The lower Chester River grew 55% (321 to 496 acres); the mouth of the Choptank grew 54% (3,214 to 4,951 acres) while the Lower Choptank segment grew 157% (10 to 25 acres) and the Little Choptank grew 337% (157 to 684 acres); the Manokin River’s mouth grew 125% (161 to 361 acres); the lower Pocomoke River grew 53% (148 to 227 acres); and the South River, though tiny in absolute terms, grew more than 1,000%, from 0.3 to 3.4 acres. The single largest gain anywhere in the Bay came in Tangier Sound segment 1, around Smith and Bloodsworth islands, which grew by more than 1,400 acres to reach 8,241. Not every area on the lower Shore gained, though — the Honga River and the Lower Central Chesapeake Bay segment together lost 1,277 acres.
Bay-wide, a story of extremes
Zooming out to the full Bay, including Virginia’s waters, the clearest gains came in the saltiest zones. Eelgrass continued expanding into deeper water as clarity improved, driving what VIMS called record abundance in the high-salinity zone. “The different stories unfolding among the salinity zones really highlights just how incredibly large and complex the Chesapeake Bay ecosystem is,” said Christopher Patrick, associate professor and director of the SAV Monitoring and Restoration Program at VIMS. “It’s never just one story; it’s a collection of stories. A good year for SAV in one river can also be a terrible year for SAV in another.” Tidal fresh zones saw a modest overall decline, driven in part by hydrilla losses in Virginia’s upper Rappahannock River, one of several rivers the Chesapeake Bay Foundation flagged alongside the Potomac, Patapsco, and Gunpowder.
Dan Coogan, director of the Chesapeake Bay Program at EPA Region 3, credited the overall progress to sustained, multi-level investment. “The growth of underwater grasses in the Bay is an encouraging sign of what sustained coordination and investment at the federal, state and local level in Bay restoration can accomplish,” Coogan said. “While this progress is important, the work is not finished until we achieve the goal of 196,600 acres.” Chesapeake Bay Foundation Virginia senior scientist Joe Wood struck a similar balance. “Increased underwater grass coverage is a clear sign of how the Bay is healing,” Wood said. “While there’s plenty to celebrate with more grasses in saltier parts of the Bay, the declines in many rivers, including the Rappahannock, reveal that significant work remains. Polluted runoff from sources like development and agriculture remains a big threat to underwater grasses, and this is exacerbated by rising temperatures and more intense storms fueled by climate change.”
Chesapeake Bay Foundation Maryland scientist Julie Luecke echoed that the uneven results demand continued action rather than celebration alone. “Underwater grass gains across the Bay are welcome news, but Maryland’s rivers tell a more complicated story,” Luecke said. “Declines in places like the Patapsco, Gunpowder, and Potomac show the pressure from polluted runoff and increasingly intense rainstorms. For thriving grasses across the region, we need more than celebration. We need action.”
Scientists caution that a single strong year doesn’t guarantee the trend continues. SAV depends on sunlight reaching the Bay floor, meaning water clarity is fundamental to its survival, and factors like nutrient and sediment runoff, algal blooms, storms, temperature, and shifting salinity can push grass beds in either direction from one year to the next.
