The Chesapeake Bay received a C+ on its annual health report card, the highest score in the 20 years the University of Maryland Center for Environmental Science has kept records. The overall score rose 6% from last year, but conditions varied widely across the watershed, and some measures of water quality declined. Eight of the Bay’s 15 regions improved, including the Patapsco and Back Rivers, the Upper Western Shore, the Rappahannock, the Lower Eastern Shore, and the Upper and Lower Bay. The Lower Bay, between Cape Henry and Cape Charles in Virginia, scored highest at B+. The Lower Western Shore, extending south from the Patapsco area toward the Patuxent River, scored D−, with urban runoff among the pressures affecting the region. Researchers found that levels of pollutants entering the Bay held steady or decreased. But water clarity worsened, as did chlorophyll a levels, which can contribute to harmful algae blooms. A recent bloom on the Eastern Shore damaged oyster farms and has been linked by the Chesapeake Bay Foundation to reports of fish kills. The report was announced Tuesday in Woodbridge, Virginia. State and environmental leaders said the results reflect the effects of ongoing cleanup and restoration, while cautioning that improvements take time. Alexandra Fries, a program manager at the center, said population growth, development, agriculture and tourism continue to put pressure on the watershed. Some of the gains may be tied to unusually dry conditions across much of the watershed. Drought meant less water flowed off farmland and through stormwater systems, carrying pollutants into rivers and the Bay. But Fries said the 6% increase was too large to attribute to low precipitation alone, and also pointed to restoration projects and improved management practices. Those efforts include oyster reef restoration. Maryland and Virginia have restored and protected about 2,400 acres of oyster habitat since the 2014 watershed agreement, with more than 7.5 billion oysters planted. Oysters filter water, though restoration does not remove the need to prevent pollution at its source. The Bay’s watershed partnership, which includes six states and Washington, D.C., has set goals for reducing sediment and nutrient pollution, improving infrastructure and promoting better agricultural practices. A revised agreement signed in 2025 sets new targets for 2040. The report also comes after major pollution events, including a February sewage-pipe break near Cabin John, Maryland, that sent an estimated 243 million gallons of raw sewage into the Potomac River. The spill led to oyster-harvest closures in some areas and calls for expanded water testing. The U.S. Environmental Protection Agency announced $37 million in grants earlier this month for watershed and nutrient-reduction projects, to be matched with another $53 million. University of Maryland center President Fernando Miralles-Wilhelm said the improving trend is a reason to maintain—and increase—investments rather than cut them. The Chesapeake Bay is the largest estuary in the United States. Its report-card gains offer evidence that cleanup measures can make a difference, but the uneven regional scores and continued threats underscore how much work remains for communities that depend on the Bay and its waterways.