The new numbers capture both how far the ecosystem has come and how much work remains. When systematic monitoring began in 1984, underwater grass coverage had collapsed to approximately 39,000 acres, the residue of decades of nutrient pollution, sediment runoff and habitat degradation that pushed the Bay’s once-extensive meadows to historic lows in the 1980s. Abundance has since more than doubled, a trajectory researchers attribute in large part to nutrient reduction measures implemented throughout the 64,000-square-mile watershed. The 2025 results suggest those sustained investments continue to pay ecological dividends, even as climate change, shifting land-use pressures and localized environmental stressors introduce new complications for restoration planners.

Christopher J. Patrick, associate professor and director of the SAV Program at VIMS & the Batten School, said the survey reflects a recovery that is both encouraging and uneven. This year’s results, he noted, demonstrate that the Bay is moving in the right direction while also revealing considerable complexity in the composition and behavior of its underwater grass communities. Strong recovery continues in the main basin, particularly in the saltier portions of the Bay, while some localized freshwater areas have experienced setbacks. Patrick emphasized that the mainstem recoveries are especially meaningful because they indicate that watershed-level management actions are producing measurable positive outcomes at the scale of the entire estuary.

Much of the 2025 increase was driven by continued expansion in the Bay’s higher-salinity waters. The Polyhaline Zone, which encompasses the saltiest waters near the Bay’s mouth, grew from 25,266 acres in 2024 to an estimated 28,142 acres in 2025, setting a new record for the second consecutive year. The moderately salty Mesohaline Zone expanded nearly 15 percent, from 33,033 acres in 2024 to an estimated 37,879 acres in 2025. Researchers attribute much of this growth, including the record-setting expansion of eelgrass meadows, to sustained year-over-year improvements in water clarity in the lower Bay. Recent work has documented consistent water-quality gains throughout the Chesapeake Bay mainstem over the past several years, and the concurrent expansion of eelgrass, both in the size of existing beds and into deeper waters, is consistent with those improvements.

Similar processes appear to be driving the expansion of widgeon grass in the middle portion of the Bay, a species that is still rebounding from a dramatic crash triggered by exceptionally wet conditions in 2018. Heavy rainfall years deliver pulses of nutrients and sediment that cloud the water and suppress the light these plants need for photosynthesis, and the 2018 event demonstrated how vulnerable even recovering beds can be to climatic variability. The fact that widgeon grass has reestablished itself in the years since underscores the resilience of these communities when the underlying conditions that govern light availability begin to stabilize. Patrick described the pace of change in the lower Bay as remarkable, noting how rapidly seagrass can recover when conditions are right and expressing hope that the Bay’s ultimate seagrass restoration goals remain achievable.

Despite the Bay-wide gains, the survey revealed distinct declines in other portions of the estuary, a reminder that aggregate statistics can mask divergent regional trajectories. The Tidal Fresh Zone, a collection of spatially isolated upstream rivers and embayments, experienced a small decline, falling from 20,221 acres to an estimated 18,653 acres. Researchers observed particularly significant losses in several Virginia tributaries, including portions of the upper Rappahannock River. These declines were driven largely by reductions in Hydrilla verticillata, an invasive aquatic plant commonly known as water thyme that has expanded and contracted across multiple river systems in recent years. Because hydrilla can dominate freshwater beds, its fluctuations can swing regional totals even when native vegetation remains comparatively stable.

The slightly salty Oligohaline Zone, by contrast, remained relatively stable overall at just over 4,700 acres, with gains in several portions of the Bay helping to offset losses elsewhere. Patrick stressed that the Bay is not a single ecosystem but a collection of many distinct habitats, each responding differently to rainfall, water quality, salinity and other environmental factors and stressors. What emerged from this year’s survey, he said, is a reminder that Bay-wide trends are really the sum of many regional stories. Researchers say these contrasting patterns highlight the complexity of restoring underwater grasses across a watershed that spans parts of six states and the District of Columbia, where geography, land use, rainfall patterns, water clarity and local environmental conditions all shape how grass beds respond from one year to the next.

The ecological stakes of this recovery extend well beyond the meadows themselves. Underwater grasses provide essential habitat for fish, blue crabs, waterfowl and countless other species, functioning as nursery grounds, foraging areas and refuge from predators. They also perform a suite of ecosystem services that directly improve water quality: absorbing excess nutrients, stabilizing sediments, reducing shoreline erosion, sequestering carbon and producing oxygen through photosynthesis. Because submerged aquatic vegetation responds quickly to changes in environmental conditions, scientists consider it one of the most sensitive and informative indicators of overall Bay health, a living gauge that integrates the effects of upstream land management, wastewater treatment, atmospheric deposition and climate variability into a single measurable signal.

Historical evidence suggests the Chesapeake Bay once supported between 200,000 and 600,000 acres of underwater grasses, a range that dwarfs today’s totals and frames the scale of the restoration challenge. The 2025 acreage of 89,385 acres, while the highest since 2018, still leaves the Bay at less than half of the 196,600-acre long-term goal. Yet the trajectory of the past four decades offers what researchers describe as genuine grounds for optimism. Recovery has proven possible, Patrick said, and the gains documented since monitoring began reflect the benefits of cleaner water and sustained restoration effort. Continuing that progress, he cautioned, will require ongoing support for science, habitat conservation and water-quality improvements throughout the watershed. For the scientists who fly the aerial surveys each year and the managers who translate the results into policy, the 2025 findings serve as both a validation of past investments and a measure of the distance still to be traveled in restoring one of the world’s largest and most closely studied estuaries.

Subject of Research: Annual monitoring of submerged aquatic vegetation recovery in the Chesapeake Bay

Article Title: Chesapeake Bay underwater grasses increase 7%, buoyed by gains in salty waters

Article References: Chesapeake Bay underwater grasses increase 7%, buoyed by gains in salty waters. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Chesapeake Bay, submerged aquatic vegetation, eelgrass, widgeon grass, water quality, seagrass restoration, water clarity, VIMS, estuary health, nutrient reduction, Polyhaline Zone, habitat restoration

Published in Regional Studies in Marine Science, the study examines how R. maritima survives in mosquito impoundments, engineered wetlands separated from the lagoon by dikes and water-control structures. These systems are managed through Rotational Impoundment Management, a process that periodically reconnects them with the lagoon. The resulting fluctuations in water level, salinity and water quality create difficult conditions for seagrasses, but they also provide a natural experiment: species that persist there must tolerate repeated environmental disruption and rapidly changing habitat conditions.

Over three years, researchers monitored naturally occurring R. maritima populations at two locations within Bee Gum Point Nature Preserve. They measured seasonal changes in plant coverage and biomass while recording environmental conditions that could influence growth and reproduction. The team also analyzed sediment samples for dormant seeds and conducted controlled laboratory experiments to determine which environmental signals trigger germination. In parallel, plants collected from the preserve were grown in aquaculture tanks at the FAU Harbor Branch Seagrass Nursery, where scientists tracked their development, flowering, seed production and potential for large-scale cultivation.

The field observations revealed that R. maritima follows a sharply seasonal annual life cycle. Plants grew mainly from late winter through spring, flowered during the warmer part of the year and then largely disappeared above the sediment during summer. This dieback could easily be mistaken for permanent local extinction. However, the population returned in subsequent years, demonstrating that the visible plants represent only one phase of a broader life-history strategy. The species’ persistence depended on what remained below the surface after the shoots and leaves had vanished.

That hidden survival system was a persistent seed bank embedded in the sediment. Seeds remained viable through periods when the impoundments experienced flooding, high salinity and deteriorating water quality, allowing the population to regenerate when conditions improved. Laboratory trials showed that reduced salinity, especially exposure to freshwater, strongly stimulated germination. The finding indicates that freshwater pulses may act as an ecological cue, signaling a temporary window in which conditions are favorable for seedlings to emerge and establish before the next period of environmental stress.

“Ruppia maritima has a remarkable ability to persist through disturbance,” said Rachel Brewton, Ph.D., senior author and an assistant research professor at FAU Harbor Branch. “Even when the plants disappear above ground, the population can persist as a seedbank in the sediment, waiting for conditions to become favorable.” This capacity is particularly significant in the Indian River Lagoon, where restoration sites may not remain stable long enough for conventional planting methods to succeed. A seed bank can preserve genetic material through unfavorable seasons and release new plants when hydrological conditions shift.

The species also performed well under nursery conditions. Plants transplanted into aquaculture tanks became established, reproduced and produced viable seeds while maintaining a seasonal growth pattern similar to that observed in the wild. Most notably, the cultivated population has remained self-sustaining since it was established in 2021. “That ability to regenerate from a persistent seed bank, combined with its successful cultivation in our seagrass nursery, is what makes this species particularly interesting from a restoration perspective,” said Richard Mulroy, a study co-author and biological scientist at FAU Harbor Branch.

The researchers say R. maritima could function as a pioneer species in degraded parts of the lagoon. Rather than replacing mature seagrass communities, it could be introduced into bare or disturbed areas where its rapid seasonal growth and tolerance of fluctuating conditions might help begin the recovery process. By stabilizing sediment, adding habitat structure and influencing local water conditions, early colonizers can potentially make sites more suitable for other seagrass species. “The goal of restoration is not simply to put seagrass back—it is to create the conditions for a functioning ecosystem to recover,” Brewton said.

The results also point toward seed-based restoration as a promising alternative or complement to transplanting adult plants. During the experiments, R. maritima seeds remained viable during prolonged exposure to high salinity and germinated after freshwater treatment, suggesting that seeds could be collected, stored and propagated before deployment. The approach could improve the timing and scale of restoration, but field trials are still needed to determine how seeds and nursery-grown plants perform under natural conditions. Researchers will next test planting methods, identify suitable environmental windows and evaluate whether the species can help rebuild seagrass habitat in the Indian River Lagoon and other disturbed estuaries. The study was supported by the U.S. Fish and Wildlife Service’s Coastal Program, with matching support from the Indian River Land Trust, and was dedicated to the memory of research professor M. Dennis Hanisak, Ph.D.

Subject of Research: Not applicable

Article Title: Ecology and restoration potential of Ruppia maritima in a managed mosquito impoundment of the Indian River Lagoon, Florida, USA

News Publication Date: 18-Jul-2026

Web References: Florida Atlantic University, https://www.fau.edu/; FAU Harbor Branch Oceanographic Institute, https://www.fau.edu/hboi/; FAU Harbor Branch Seagrass Nursery, https://www.fau.edu/hboi/research/marine-ecosystem-conservation/coral-reefs/seagrass-nursery-and-marine-botany/

References: Regional Studies in Marine Science, DOI: 10.1016/j.rsma.2026.105271

Image Credits: FAU Harbor Branch

Keywords: Seagrasses, Ruppia maritima, Indian River Lagoon, seagrass restoration, seed banks, marine conservation, aquatic ecology, water quality, ecological resilience, aquaculture, mosquito impoundments, estuaries