Bay Grass Report shows mixed results

Results from the 2024 Submerged Aquatic Vegetation (SAV) Survey of the Chesapeake Bay show mixed outcomes, essentially staying flat. Conducted by William & Mary’s Batten School of Coastal & Marine Sciences and the Virginia Institute of Marine Science (VIMS), the annual survey recorded a 1% net decline in SAV coverage, totaling 82,778 acres — 641 acres less than in 2023.

According to researchers, the Bay’s current SAV coverage represents 64% of the 2025 restoration target and 45% of the long-term goal of 185,000 acres set by the Chesapeake Bay Program (CBP). Coverage is assessed across four salinity zones, each with its own target. This year’s results showed varied outcomes by region.

The Polyhaline Zone, which includes the Bay’s saltiest waters, recorded a 14% increase in SAV coverage, reaching a record 24,800 acres—74% of that zone’s goal. This is the highest coverage recorded in the region since annual mapping began in 1984. Growth in this zone was largely driven by eelgrass expansion in areas such as Mobjack Bay, Poquoson Flats, and parts of Maryland’s Western Shore.

The Tidal Fresh Zone also saw progress, with a 2% increase to 20,218 acres—98% of its target. The Oligohaline Zone experienced a 38% increase, growing to 4,730 acres, or 46% of its goal. Recoveries in tributaries such as the Sassafras, Gunpowder, Back, and Middle Rivers, and the upper Potomac contributed to these gains.

In contrast, the Mesohaline Zone—the Bay’s largest and most diverse region—declined by 14%, falling from 38,371 acres to 33,031 acres. That area now meets just 27% of its target of 120,306 acres. Losses were most significant along Maryland’s Eastern Shore, including the Choptank and Little Choptank Rivers and Tangier Sound. Researchers attribute the decline to increased freshwater input, high nutrient loads, and reduced salinity, which negatively impacted widgeon grass.

Despite the decline in overall acreage, CBP officials emphasized the importance of long-term nutrient reduction and continued restoration. Brooke Landry, chair of the CBP’s SAV Workgroup and SAV program chief at the Maryland Department of Natural Resources, stated that “increases in SAV acres observed in three of the four salinity zones this year are truly a testament to the effectiveness of long-term nutrient reductions and collaborative restoration efforts.”

SAV is a critical ecological indicator of Bay health, providing habitat, protecting shorelines, filtering nutrients, and sequestering carbon. The VIMS SAV Monitoring and Restoration Program, in partnership with the CBP, has tracked underwater grasses since 1978, and overall coverage has more than doubled since then.

The CBP has released a draft update to the Chesapeake Bay Watershed Agreement, which proposes a revised Bay-wide SAV goal of 196,000 acres by 2035, with an interim target of 95,000 acres. Public comment on the draft is open through September 1 via the CBP’s Beyond 2025 webpage.