This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Submerged aquatic vegetation (SAV), one of the Chesapeake Bay's most important indicators of ecosystem health, increased by 7% in 2025, according to researchers at William & Mary's VIMS & Batten School. The annual Baywide aerial survey reported a total of 89,385 acres (140 square miles) of underwater grasses in the Chesapeake Bay and its tidal tributaries, an increase of 6,134 acres (9.6 square miles) from 2024.
The results represent the highest Baywide acreage recorded since 2018. The total is just shy of the Chesapeake Bay Watershed Agreement's 2030 interim goal of 90,000 acres (141 square miles) and represents approximately 45% of the 196,600-acre (307-square-mile) long-term goal. The results highlight the substantial progress made since underwater grass coverage reached historic lows in the 1980s and the challenges that remain to fully restore one of the Bay's most valuable habitats.
"This year's survey demonstrates both that we're moving in the right direction and that there is a lot of complexity in Chesapeake Bay underwater grass communities," said Christopher J. Patrick, associate professor and director of the SAV Program at VIMS & the Batten School of Coastal & Marine Sciences. "We continue to see strong recovery in the main basin, particularly the saltier portions of the Bay, with some setbacks experienced in localized freshwater areas.
The mainstem recoveries are particularly encouraging, as they are indicative of watershed-level management yielding positive outcomes." Much of the Baywide increase was driven by the continued expansion of underwater grass beds in higher-salinity waters. The Polyhaline Zone, which includes the Bay's saltiest waters near its mouth, increased from 25,266 acres (39 square miles) in 2024 to an estimated 28,142 acres (44 square miles) in 2025, setting a new record for the second consecutive year. The moderately salty Mesohaline Zone expanded nearly 15%, from 33,033 acres (52 square miles) in 2024 to an estimated 37,879 acres (59 square miles) in 2025.
Researchers attribute much of that growth, and the record-setting expansion of eelgrass, to sustained year-over-year increases in water clarity in the lower Bay. Recent work has demonstrated consistent improvements in water quality throughout the entire Chesapeake Bay mainstem over the past several years. The concurrent expansion of eelgrass meadows, both in size and into deeper waters, is consistent with those improvements.
Similar processes are likely also driving the expansion of widgeon grass in the middle portion of the Bay, which is still recovering from a crash due to exceptionally wet conditions in 2018. "It's been remarkable to watch how fast the lower Bay meadows are expanding right now," Patrick said. "It's another example of how rapidly seagrass can recover when conditions are right and gives us hope that the ultimate seagrass restoration goals for the Chesapeake Bay remain achievable." Despite the overall increase, the survey revealed distinct declines in other portions of the Bay.
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