Chris Patrick is optimistic about seagrass restoration.
“There are lots of kinds of restoration happening in the world — mangroves, oyster reefs, forests, coral reefs,” says the director of the aquatic vegetation restoration program at Virginia Institute of Marine Science. “But seagrass is one of the only systems I can think of where it happens very fast if conditions are right. You get a 15 to 1 return. For every acre planted, 15 acres grow. Some restored areas look like they did 100 years ago.”
What a difference a century can make.
Since the early 1900s, vast coastal seagrass meadows — think of underwater fields of long, swaying plants that host hundreds of nearby marine species — have dwindled and even disappeared around the world. They’ve succumbed to a growing list of insults that includes thermal stress from climate change, dredging, coastal development, intentional removal, disease, and increasing pollution runoff from agriculture and other human activities.
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Because seagrasses live below the water, out of sight, the magnitude of the loss has only recently begun to sink in. A 2020 study reported a global net loss of 29% or more than 19,000 square miles (about the size of Costa Rica). The western Gulf of Mexico alone saw a 23% decline and parts of the United Kingdom 44%.
On the other hand, scientists restoring these coastal ecosystems see more success than with other marine environments. Collecting seeds and placing them in suitable habitat is generating the most positive results along the U.S. East Coast and elsewhere.
Why Seagrass Matters
Seagrasses — which evolved from terrestrial plants — have roots, stems, and leaves and produce flowers and seeds. They form vast underwater meadows that provide multiple ecosystem services such as habitat for a variety of marine animals. They provide foraging and spawning grounds for dugong and sea turtles and shelter for fish and invertebrates.
Seagrasses also are nursery habitat — key areas for young animals to grow — for over 20% of the world’s largest fisheries, according to information provided via email by the UK-based conservation group Project Seagrass. One study estimated that the UK’s historical seagrass meadows could have supported about 400 million fish. Today its remaining meadows support approximately 50 million.
Project Seagrass also notes that the plants improve water quality by filtering out pathogens, bacteria, and pollution.
The plants also benefit the planet as a whole: They sequester up to 18% of carbon stored in the ocean, capturing it 35 times faster than tropical rainforests.
The roots of seagrasses strengthen the seafloor and, along with their leaves, weaken wave energy and storm surges to help protect coastal communities. This slowing of waves also causes sediment to drop out of the water, feeding bacterial communities that metabolize nitrogen compounds and reducing excess nutrients in the water that can lead to algal blooms and low oxygen levels.
Spreading Seeds
Damaged meadows can regenerate on their own from pockets of surviving plants — but only if what caused the damage passes or is removed and only in areas close enough to be reseeded by those survivors.
That happened along much of the U.S. East Coast after a disease in the 1930s wiped out about 99% of the most common species, Zostera marina, or eelgrass, Patrick says.
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But regeneration never happened on Virginia’s coast, where bays are too isolated from each other to be reseeded by survivors outside of them.
Today these bays have the right conditions for seagrass growth, though, which made them natural targets for restoration efforts. In 1999 scientists from the University of Virginia’s Coastal Research Center, The Nature Conservancy, and VIMS distributed more than 70 million seeds in these bays. To date the effort has created new meadows covering more than 10,500 acres.
With funding from NOAA, the participants seeded another 80 acres in Burton’s Bay in fall 2023 and another 45 acres in fall 2024. Teams also have set up stations to collect water quality data and to monitor marine life. The project is set up to be funded through 2027 and has not yet been affected by the general threat to all federal funding under the Trump administration.
A Garden Experiment
Another effort kicked off in 2022. A series of workshops hosted by The Nature Conservancy brought together experts on seagrasses, corals, agriculture, forestry, and plant genetics to explore restoration strategies used for other ecosystems.
“We went to forestry groups, coral groups, all these different silos to find out their thinking,” says Boze Hancock, senior marine restoration scientist with The Nature Conservancy’s global oceans team. “Forestry and grassland groups are dealing with the same thing on land: changes happening too fast for natural adaptation to keep up. But different strains of plants on different hills and mountains at different latitudes have a lot of adaptations to test. The quickest way to look at all the variables and tease out which ones work in your area is a common garden experiment.”
This strategy grows populations from the same species collected from different regions and microclimates under common conditions to see how they respond. Scientists can use that information to identify strains more likely to thrive in specific conditions and then strategically relocate them, a process called assisted migration. This technique also is being used in coral restoration.
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Growing seagrasses from different latitudes along the East Coast in a common garden could help match genetic tolerance to conditions such as water temperature and pollution in specific locations, explains Hancock. A population thriving in a Virginia estuary today, for example, might be suited for the warming waters of Long Island in the future.
Scientists from national parks and National Estuarine Research Reserves on the East Coast, University of Maryland Center for Environmental Science, University of North Carolina Wilmington, Stony Brook University, and other involved groups plan to use those “most likely to succeed” strains in restoration.
Using seeds allows scaling up of restoration efforts. That, says Hancock, is key to keeping up with the rapid rate of change.
“Back in the 1980s, [seagrass] restoration tended to be slow and steady, transplanting root stock one plot at a time.”
Across the Pond
Over on the other side of the Atlantic, the same list of insults killed off as much as 92% of seagrass meadows in the UK during the past century, according to Project Seagrass.
In 2019 the organization, along with Swansea University and the nonprofit Pembrokeshire Coastal Forum, piloted the UK’s first major seagrass restoration project, “Seagrass Ocean Rescue: Dale,” off the southwest coast of Wales. According to information provided by Corrinne Cox, communications officer at Project Seagrass, the effort collected and planted over 1 million Z. marina seeds on 2 hectares (almost 5 acres).
The team chose the site based on habitat suitability modelling and historic and anecdotal records indicating the Welsh coast had much more extensive seagrass historically than now. Seeds were hand-collected primarily in North Wales by scuba divers, snorkelers, and people wading at low tide.
According to Cox the project collected and processed an estimated 750,000 seeds in summer 2019 and another 450,000 in summer 2020. They used the Hessian Bag method, which places a mixture of seagrass seeds and sterile sand into containers made of vegetable fibers (also known as burlap) ready for planting.
Project Seagrass worked with volunteer groups throughout the UK to prepare the bags. Community support and commitment has been key to the effort, according to Cox, and representatives from the local community continue to guide management of the seagrass, along with users of coastal waters and regulators.
Monitoring and More
Monitoring whether efforts are successful and what adjustments may be needed for subsequent projects is key to restoration. Monitors typically measure total area covered and number of shoots per square meter.
“Basically, if it is growing in area and thickness, it’s working,” Hancock says. “It’s not rocket science. It is complicated somewhat by the fact that eelgrass grows during spring and summer and tends to die back in the fall. So the timing of monitoring is important, as is repeating it over years.”
Ongoing monitoring in Dale, for example, showed a threefold increase in shoot density throughout the restoration area by fall 2024, Cox reports. Scientists also saw increased shoots per clump and clumps more than eight times larger on average from two years before, showing that the grass is spreading.
Some projects engage citizen scientists. Anglers, divers, beach goers, and other visitors to coastal waters can report sightings of seagrass on the Project Seagrass app, SeagrassSpotter. The app is a way to expand the number of people contributing to mapping distribution and status of the plants from a few hundred scientists to hundreds of community members.
People also can help by taking action on climate change and encouraging others to do so — important today more than ever. Individuals can support community efforts to switch to clean energy or ramp up public transportation, buy products from companies with sustainable practices (and buy less overall), or donate to and volunteer with projects restoring habitats like seagrass that sequester carbon.
Boze adds that another way to help is by reducing excess nutrients in coastal bays by avoiding use of fertilizers on lawns or commercial properties.
The recreational boating community can help reduce physical damage to seagrass from anchoring and mooring. The Dale project installed three moorings as an alternative to anchoring for visiting boats and encourages users to donate to support the upkeep of the buoys.
In a world where many species and habitats continue to decline, these attempts to bring back seagrass offer a ray of hope. Restoring seagrass habitat takes a lot of effort, the experts admit. But with the right conditions, tiny sesame-sized seagrass seeds can lead to massive results — not just for seagrass itself, but for everything and everyone that depends on it.
