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NEW BEDFORD — Just after sunrise, Tessa Peixoto and Heather Cyr plunged into Clarks Cove, pumping air through their snorkels as they swam several yards offshore. Cyr carried a waterproof notebook and pen; Peixoto, a pair of square metal frames. Beneath them, bubbles rose from ribbon-like eelgrass leaves, crackling as they reached the surface.
Peixoto dropped a frame onto the dark-green meadow below. She dove to count the light-green branches on eelgrass shoots within its bounds. She resurfaced holding a shoot with a yellow-green branch, which was filled with tiny seeds.
”17,” she said. Cyr jotted the number down.
The Massachusetts Division of Marine Fisheries seasonal technicians were gathering data for a study on the seed-producing capacity of Buzzards Bay eelgrass beds — critical for healthy coastal ecosystems and communities. DMF is also looking at the timing of the reproductive cycle for eelgrass in these underwater meadows.
The first of two field work seasons ran from April into August. Massachusetts fisheries researchers are analyzing the data this fall and winter.
The work will help the state determine if seed-based eelgrass restoration is feasible in Buzzards Bay. It’s a practice that could help rebuild this productive ecosystem in local waters, after decades of decline.
“Eelgrass is so often unseen,” said Forest Schenck, a DMF marine fisheries habitat specialist and the lead researcher on the project. “But it’s really key to coastal systems, and part of what makes Massachusetts, Massachusetts.”
Eelgrass grows in shallow waters along the Massachusetts coastline, including Buzzards Bay. It produces oxygen for marine life. It provides habitat for juvenile fish, invertebrates, and shellfish — like bay scallops.
The seagrass improves water quality and stabilizes coastal sediment. It absorbs energy from waves during storms. It can capture and store large amounts of carbon at a faster rate than tropical rainforests.
Since the 1990s, eelgrass beds have declined across the state and in Buzzards Bay. DMF estimates Massachusetts has lost roughly half of its eelgrass since the 1990s. Buzzards Bay eelgrass beds declined from roughly 7,500 acres in 1997 to roughly 6,000 acres in 2021, according to a Buzzards Bay National Estuary Program analysis.
Much of the eelgrass loss in Buzzards Bay is tied to nitrogen pollution.
Eelgrass needs clear water and light to survive. Human waste, fertilizers, and impervious surfaces in communities around Buzzards Bay contribute nitrogen to local waters. It enters the bay in stormwater runoff, and through groundwater — which feeds rivers and streams.
Nitrogen naturally occurs in coastal ecosystems, yet too much causes algae to bloom in the water. That makes the water murky, restricting sunlight to eelgrass beds and causing them to die off.
Many of the major harbors, coves, and tidal rivers of Buzzards Bay are dealing with long-term water quality challenges due to nitrogen pollution. A lot of those waters have seen a decline of eelgrass beds.
Boating structures like floats and docks can also block light to these meadows. Chains from moorings can scour the seafloor and kick up sediment, hurting eelgrass.
Eelgrass beds have been recovering in some parts of Buzzards Bay in recent years. Surrounding communities have been cutting their nitrogen loads. Federal air pollution regulations have limited the nitrogen entering the bay from vehicle and industrial emissions.
Still, natural recovery of these meadows is slow. Eelgrass has been declining in other parts of Buzzards Bay. Reducing the impacts of nitrogen pollution may become more difficult with climate change and warming bay waters.
Massachusetts has been working to help eelgrass beds recover along the coastline in recent decades, through adult shoot transplants — planting plugs or shoots of adult eelgrass in sediment beds at a restoration site.
Yet these projects are expensive and labor-intensive, requiring trained divers. Coordinating large-scale adult shoot transplant efforts is difficult.
That’s why Massachusetts is now exploring seed-based restoration for eelgrass beds in Buzzards Bay, a method that is showing promise in the mid-Atlantic.
Seed-based eelgrass restoration involves harvesting seeds from flowers in local “donor” meadows, and redistributing these seeds on target restoration sites.
Potential eelgrass seed harvesting sites
Eelgrass seeds sink to the seafloor after they are released by their parent plant. They can be harvested and planted at restoration sites in easier and cheaper ways than adult shoots. So seed-based methods may open up opportunities for large-scale restorations, with a wide network of collaborators, Schenck said.
Yet these restoration projects require hundreds of thousands — if not millions — of eelgrass seeds over multiple years. Eelgrass seeds cannot be stored for more than a couple of months, Schenck added. So practitioners will have to re-up their seeds annually from local donor meadows to conduct long-term restorations.
Massachusetts does not know whether eelgrass beds in Buzzards Bay are producing seeds at a high enough capacity to support local restoration projects. It also does not know when the best times in the season are to harvest eelgrass seeds from Buzzards Bay meadows.
So this year, Schenck’s team went out every two weeks to monitor six Buzzards Bay eelgrass beds during the reproductive season, from the spring through the summer.
The sites are at Clarks Cove in New Bedford, West Island in Fairhaven, Onset Beach in Wareham, and Wings Cove in Bourne, along with Little Island and Woods Hole Waterfront Park in Falmouth.
The researchers are looking at the timing of phases in the reproductive cycle for eelgrass plants at these locations.
They are also gathering information on the traits of eelgrass plants across sites. That includes data like the ratio of leaves to reproductive branches on eelgrass shoots, the average number of seeds in reproductive branches, and the density of shoots and reproductive branches in the meadows.
DMF scientists are interested in how these data may relate to water temperature, light, and water quality in the different eelgrass beds during the season.
“It’s really about trying to identify sites that could be really good donors,” Schenck said.
Preliminary data shows that all of the sites that DMF has looked at in Buzzards Bay seem capable of supporting seed-based eelgrass restoration efforts.
Schenck said his team is also seeing differences in peak flowering and seed production times across Buzzards Bay eelgrass beds.
The meadows near the outer points of Buzzards Bay — like the one at Woods Hole Waterfront Park — seem to reach those benchmarks later than sites tucked farther into the bay, like West Island.
The DMF team will use this data to develop a model that predicts when peak flowering and seed production times are happening in eelgrass beds across Buzzards Bay.
The Rhode Island Department of Environmental Management is partnering with DMF on this project, and conducting a similar study of six Rhode Island eelgrass beds.
Schenck said the work these partners are doing will help solve the larger puzzle of restoring eelgrass across southern New England long-term.
“It’s been part of our systems for millennia,” he said. “Being able to sustain that and preserve that for Massachusetts 50 years from now, and 100 years from now, is intrinsically important.”
Email reporter Adam Goldstein at agoldstein@newbedfordlight.org.
