Mapping the Decline of
Eelgrass Along Maine’s Coast
Researchers are studying the role of eelgrass beds for carbon capture
and the health of the habitat for a variety of species.
Summary Eelgrass serves many roles in coastal environments, including preventing shoreline erosion and providing a habitat for sea creatures.
By Murray Carpenter, September 17, 2024
A light wind kicks up sparkling wavelets while lobster boats weave among granite islets, with ospreys and a bald eagle soaring overhead.
Cheyenne Adams ignores those surroundings, motoring along slowly on a 21-foot boat. She stares intently at a video screen that reveals a patch of deep-green grass waving in the current just eight feet below the hull.
A light wind kicks up sparkling wavelets while lobster boats weave among granite islets, with ospreys and a bald eagle soaring overhead.
Cheyenne Adams ignores those surroundings, motoring along slowly on a 21-foot boat. She stares intently at a video screen that reveals a patch of deep-green grass waving in the current just eight feet below the hull.
[Adams is a Biologist II, Managing MDEP's Marine Vegetation Mapping Program in Maine DEP's Bureau of Water Quality
“There’s eelgrass,” Ms. Adams said. “There’s another little patch of grass, and now we’re getting into the bed. This is a healthy bed.”
Eelgrass, or Zostera marina, is widely distributed in the Northern Hemisphere. Along the Atlantic coast of the United States, eelgrass primarily thrives from Chesapeake Bay to Maine, but it is declining quickly.
Often overlooked because it is underwater, out of sight, the flowering plant plays an important role in coastal environments that is increasingly capturing the attention of researchers.
Physically, eelgrass clarifies water by trapping sediment and protecting shorelines from erosion. Chemically, it buffers ocean acidification through respiration and removes nitrogen that can fuel excess algae growth. And, ecologically, eelgrass meadows provide habitats for dozens of species, including striped bass, lobsters, blue crabs, bay scallops and blue mussels. Other species, including brant, forage on the grass.
Image
Cheyenne Adams of the Maine Department of Environmental Protection, surveying eelgrass along a coastal region in Maine.Credit...Tristan Spinski for The New York Times
Its abilities to sequester and store carbon — part of the blue carbon system in vegetative coastal environments — are increasingly catching the attention of climate researchers.
Ms. Adams and her team at the Maine Department of Environmental Protection are surveying eelgrass along the entire coast of Maine, working west to east, covering a fifth of the coast each year. First, a spotter plane flies over the coast to identify possible meadows. Then the boat runs hundreds of transects, using an underwater video camera to validate the patches viewed from the air.
The survey conducted in midcoast Maine in 2023 showed a 60 percent decline in eelgrass since 2005. In one stark example, eelgrass in the Medomak River estuary dropped from 533 acres to none. And one day this summer in northern Penobscot Bay, Ms. Adams and her team couldn’t find a single blade of eelgrass.
About half of the transects the team checks have eelgrass. At some others, Ms. Adams sees kelp and other seaweed, but no eelgrass.
“It’s the nature of the work that we don’t see grass at every transect,” she said.
Image
Eelgrass provides a habitat for species such as lobsters and striped bass.Credit...Marine Vegetation Mapping Program, Maine Department of Environmental Protection
On another day in August, Angela Brewer, who also studies eelgrass for the state’s environmental protection department, and Phil Colarusso, a marine biologist with the U.S. Environmental Protection Agency, wriggle out of their wet suits after diving in Portland Harbor to assess experimental moorings designed to coexist with eelgrass.
Dr. Colarusso keeps a busy schedule. The week after diving in Portland Harbor, he was diving near Woods Hole, Mass., one day and then near Groton, Conn. the next. He organizes an annual conference called Zosterapalooza.
Last year, Dr. Colarusso was a co-author of an E.P.A. report on blue carbon that cited findings that eelgrass meadows, along with adjacent salt marshes, sequester four to 10 times as much carbon as an equivalent area of forest. The report found that the Northeast coast, from New York to Maine, had more than 200,000 acres of eelgrass meadows and salt marshes. They are estimated to store 7,523,568 megagrams of blue carbon, which roughly equals the annual carbon emissions from six million passenger vehicles.
Dr. Colarusso said that while eelgrass is clearly a carbon-sequestration superstar, there are gaps in data. He would like to have a better understanding of the amount of carbon that eelgrass sequesters, both through primary production and through capturing organic matter. Another big question: What happens to the sequestered carbon in eelgrass beds when the eelgrass dies?
Image
Eelgrass can sequester four to 10 times as much carbon as an equivalent area of forest.Credit...Tristan Spinski for The New York Times
A changing climate poses other obstacles to maintaining healthy eelgrass.
“Stress is cumulative,” Dr. Colarusso said, “including decreased water clarity and increased temperatures.”
Over 14 years of studying Maine’s coast, Ms. Brewer has witnessed significant declines. A report last year found that eelgrass meadows in Casco Bay, near Portland, had diminished by more than half in just five years. The greatest loss is occurring in the upper reaches of estuaries, where decreased water clarity prevents sunlight from reaching the grass, Ms. Brewer said.
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Also harmful are invasive green crabs, Ms. Brewer said, because they shear off the grass, and undermine the rhizomes by burrowing for shelter.
Other factors include the increasing severity of coastal storms that can batter the grass beds. Last winter, erosion from storms smothered a Casco Bay eelgrass bed with sediment.
The grass is also susceptible to a wasting disease. In the 1930s, damage from the disease was so extensive that it caused the extinction of a snail known as the eelgrass limpet.
Image
A survey last year showed a 60 percent decline in eelgrass in midcoast Maine over about two decades.Credit...Tristan Spinski for The New York Times
Jamie Carter, a physical scientist with the coastal management office of the National Oceanic and Atmospheric Administration, has been using lidar to map coastal features, including eelgrass.
“Sea level rise is occurring — it’s going to accelerate in the future,” Mr. Carter said, adding that researchers want to understand how that will affect the health of habitats for species like eelgrass.
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Ms. Adams hopes that mapping will lead to eelgrass conservation and restoration, along with a better understanding of its roles in carbon sequestration and storage.
“There are so many things that are important about eelgrass, but you can’t see it unless you’re scuba diving, snorkeling or have an underwater camera,” Ms. Adams said. “I would say it’s undervalued in Maine, and probably globally as well.”
“There’s eelgrass,” Ms. Adams said. “There’s another little patch of grass, and now we’re getting into the bed. This is a healthy bed.”
Eelgrass, or Zostera marina, is widely distributed in the Northern Hemisphere. Along the Atlantic coast of the United States, eelgrass primarily thrives from Chesapeake Bay to Maine, but it is declining quickly.
Often overlooked because it is underwater, out of sight, the flowering plant plays an important role in coastal environments that is increasingly capturing the attention of researchers.
Physically, eelgrass clarifies water by trapping sediment and protecting shorelines from erosion. Chemically, it buffers ocean acidification through respiration and removes nitrogen that can fuel excess algae growth. And, ecologically, eelgrass meadows provide habitats for dozens of species, including striped bass, lobsters, blue crabs, bay scallops and blue mussels. Other species, including brant, forage on the grass.
Image
Cheyenne Adams of the Maine Department of Environmental Protection, surveying eelgrass along a coastal region in Maine.Credit...Tristan Spinski for The New York TimesIts abilities to sequester and store carbon — part of the blue carbon system in vegetative coastal environments — are increasingly catching the attention of climate researchers.
Ms. Adams and her team at the Maine Department of Environmental Protection are surveying eelgrass along the entire coast of Maine, working west to east, covering a fifth of the coast each year. First, a spotter plane flies over the coast to identify possible meadows. Then the boat runs hundreds of transects, using an underwater video camera to validate the patches viewed from the air.
The survey conducted in midcoast Maine in 2023 showed a 60 percent decline in eelgrass since 2005. In one stark example, eelgrass in the Medomak River estuary dropped from 533 acres to none. And one day this summer in northern Penobscot Bay, Ms. Adams and her team couldn’t find a single blade of eelgrass.
About half of the transects the team checks have eelgrass. At some others, Ms. Adams sees kelp and other seaweed, but no eelgrass.
“It’s the nature of the work that we don’t see grass at every transect,” she said.
Image
Eelgrass provides a habitat for species such as lobsters and striped bass.Credit...Marine Vegetation Mapping Program, Maine Department of Environmental ProtectionOn another day in August, Angela Brewer, who also studies eelgrass for the state’s environmental protection department, and Phil Colarusso, a marine biologist with the U.S. Environmental Protection Agency, wriggle out of their wet suits after diving in Portland Harbor to assess experimental moorings designed to coexist with eelgrass.
Dr. Colarusso keeps a busy schedule. The week after diving in Portland Harbor, he was diving near Woods Hole, Mass., one day and then near Groton, Conn. the next. He organizes an annual conference called Zosterapalooza.
Last year, Dr. Colarusso was a co-author of an E.P.A. report on blue carbon that cited findings that eelgrass meadows, along with adjacent salt marshes, sequester four to 10 times as much carbon as an equivalent area of forest. The report found that the Northeast coast, from New York to Maine, had more than 200,000 acres of eelgrass meadows and salt marshes. They are estimated to store 7,523,568 megagrams of blue carbon, which roughly equals the annual carbon emissions from six million passenger vehicles.
Dr. Colarusso said that while eelgrass is clearly a carbon-sequestration superstar, there are gaps in data. He would like to have a better understanding of the amount of carbon that eelgrass sequesters, both through primary production and through capturing organic matter. Another big question: What happens to the sequestered carbon in eelgrass beds when the eelgrass dies?
Image
Eelgrass can sequester four to 10 times as much carbon as an equivalent area of forest.Credit...Tristan Spinski for The New York TimesA changing climate poses other obstacles to maintaining healthy eelgrass.
“Stress is cumulative,” Dr. Colarusso said, “including decreased water clarity and increased temperatures.”
Over 14 years of studying Maine’s coast, Ms. Brewer has witnessed significant declines. A report last year found that eelgrass meadows in Casco Bay, near Portland, had diminished by more than half in just five years. The greatest loss is occurring in the upper reaches of estuaries, where decreased water clarity prevents sunlight from reaching the grass, Ms. Brewer said.
AdvertisementSKIP ADVERTISEMENT
Also harmful are invasive green crabs, Ms. Brewer said, because they shear off the grass, and undermine the rhizomes by burrowing for shelter.
Other factors include the increasing severity of coastal storms that can batter the grass beds. Last winter, erosion from storms smothered a Casco Bay eelgrass bed with sediment.
The grass is also susceptible to a wasting disease. In the 1930s, damage from the disease was so extensive that it caused the extinction of a snail known as the eelgrass limpet.
Image
A survey last year showed a 60 percent decline in eelgrass in midcoast Maine over about two decades.Credit...Tristan Spinski for The New York TimesJamie Carter, a physical scientist with the coastal management office of the National Oceanic and Atmospheric Administration, has been using lidar to map coastal features, including eelgrass.
“Sea level rise is occurring — it’s going to accelerate in the future,” Mr. Carter said, adding that researchers want to understand how that will affect the health of habitats for species like eelgrass.
AdvertisementSKIP ADVERTISEMENT
Ms. Adams hopes that mapping will lead to eelgrass conservation and restoration, along with a better understanding of its roles in carbon sequestration and storage.
“There are so many things that are important about eelgrass, but you can’t see it unless you’re scuba diving, snorkeling or have an underwater camera,” Ms. Adams said. “I would say it’s undervalued in Maine, and probably globally as well.”
