2025 Preliminary SAV Executive Summary
The 2025 distribution of submerged aquatic vegetation (SAV) in Chesapeake Bay and its tributaries was mapped from aerial multispectral digital imagery and satellite imagery. The aerial imagery was acquired between June and November 2025, with a resolution of 24 cm, encompassing 203 flight lines.
Chesapeake BayFor 2025, XX hectares (XX acres) of SAV were mapped in Chesapeake Bay and its tributaries and SAV increased XX% relative to 2024 from XX ha (XX ac) to XX ha (XX ac) in the regions mapped for both years. In order to ensure a valid analysis of change in SAV distribution and abundance with 2024, all direct comparisons to previous years in this report are restricted to only those regions that were mapped in both 2024 and 2025. Due to a combination of extended poor weather conditions, access restrictions, equipment failure, and the Federal goverment shutdown usable aerial imagery was not acquired in 2025 for several portions of the Bay. Comercial satellite imagery provide some coverage, but some areas, including portions of the Virginia Eastern Shore, Chickhominy River, Mattaponi, and Pamunkey rivers were not fully covered. The area that was not fully mapped in 2025 supported 2,110.8 hectares of SAV in 2024 (5,216 acres, 6.3% of the Bay total). Additional imagery was acquired from Maxar and [Planet Labs] in order to provide a more complete dataset for Chesapeake Bay. These imagery sources and their locations are detailed below:
SAV increased in two salinity zones (Mesohaline, and Polyhaline) and decreased in the other salinity zone (Tidal Fresh, Oligohaline). In 2025, SAV increased in 40, decreased in 19, and remained unvegetated in 34 of the 93 CBP segments.
Significant increases and simultaneous decreases in different regions of the bay resulted in a small net increase in total SAV coverage between 2024 and 2025 (XX% increase, XX hectares, XX acres). The Polyhaline and Mesohaline zones saw significant increases in SAV, there was a modest decrease in the Oligohaline zone, and the Tidal Fresh zone suffered significant declines. The Polyhaline zone increased 13% relative to 2024 (1,164 hectares, 2,875 acres). Segments across the Polyhaline all increased with the largest gains (hectares/acres) occurring in Mobjack Bay, Poquoson Flats, and nearby Western Shore areas. Significantly, this is the most SAV reported in the Polyhaline Zone in the history of the survey, surpassing the record set last year. [nees an edit below here] These gains, largely attributable to eelgrass, add to a pattern of consecutive year over year increases in the Polyhaline since the 2019 crash and extension of the meadows into deeper waters. This may indicate improved water clarity in this area of the Bay. The Tidal Fresh Zone was stable, exhibiting a 2% increase (149 hectares, 369 acres) and the Oligohaline Zone showed a 46% increase (584 hectares, 1,442 acres), driven by simultaneous recoveries in multiple areas including the Sassafras, Gunpowder, Back, and Middle Rivers, as well as increases in observed SAV in the Potomac River. In contrast, the Mesohaline underwent a 14% decline (-2,161 hectares, -5,340 acres), which largely occurred along the Eastern Shore of Maryland in the Choptank (-895 hectares, -2,212 acres) and Little Choptank Rivers (-302 hectares, -746 acres) as well as Tangier Sound (-801 hectares, -1,979 acres). The declines in the Choptank mirror measured reductions in water quality within the river, highlighting the strong coupling between water quality and SAV within the Chesapeake Bay, and down-bay declines in Tangier Sound may be connected. These contrasting changes observed throughout the system reflect the incredible diversity of geographic regions, land-use regimes, SAV species, and local environmental conditions that contribute in aggregate to Baywide SAV status each year. |
Tidal Fresh Bay Salinity ZoneIn the Tidal Fresh Bay Zone (19 CBP segments), 7,140 hectares (17,643 ac) of SAV were mapped for 2025. Comparing the same mapped regions between 2024 and 2025, SAV decreased 8% from 7,775 hectares (19,212 ac) in 2024 to 7,140 hectares (17,643 ac) in 2025. None of the 19 segments increased by at least 20% and by at least 5 ha from 2024 totals: Three of the 19 segments decreased by at least 20% and by at least 5 ha from 2024 totals:
Nine of the 19 segments remained unvegetated in 2025. |
Oligohaline Bay Salinity ZoneIn the Oligohaline Bay Zone (25 CBP segments), 1,836 hectares (4,538 ac) of SAV were mapped for 2025. Comparing the same mapped regions between 2024 and 2025, SAV decreased 0.4% from 1,844 hectares (4,557 ac) in 2024 to 1,836 hectares (4,538 ac) in 2025. Seven of the 25 segments increased by at least 20% and by at least 5 ha from 2024 totals:
Four of the 25 segments decreased by at least 20% and by at least 5 ha from 2024 totals:
Nine of the 25 segments remained unvegetated in 2024. |
Mesohaline Bay Salinity ZoneIn the Mesohaline Bay Salinity Zone (41 CBP segments), XX hectares (XX ac) of SAV were mapped for 2025. Comparing the same mapped regions between 2024 and 2025, SAV inreased XX% from XX hectares (XX ac) in 2024 to 1,836 hectares (XX ac) in 2025. Eleven of the 41 segments increased by at least 20% and by at least 5 ha from 2024 totals:
Three of the 41 segments decreased by at least 20% and by at least 5 ha from 2024 totals:
Fourteen of the 41 segments remained unvegetated in 2024. |
Polyhaline Bay Salinity ZoneIn the Polyhaline Bay Salinity Zone (8 CBP segments), 10,466 hectares (25,862 ac) of SAV were mapped for 2025. Comparing the same mapped regions between 2024 and 2025, SAV increased 13% from 9,302 hectares (22,986 ac) in 2024 to 10,465 hectares (25,862 ac) in 2025. None of the 8 segments increased by at least 20% and by at least 5 ha from 2024 totals. None of the 8 segments decreased by at least 20% and by at least 5 ha from 2024 totals. One of the 8 segments remained unvegetated in 2025. |