
From The Lamont-Doherty Earth Observatory
In

The Earth Institute
At

Columbia University
1.25.23
Olga Rukovets
Researchers at Columbia Climate School discuss the benefits and challenges of working with carbon from ocean and coastal ecosystems.
Blue carbon is becoming an increasingly popular term, but what exactly does it mean? The answer may vary slightly depending on who you ask. But broadly speaking, according to the National Ocean Service, “blue carbon is simply the term for carbon captured by the world’s ocean and coastal ecosystems.”
So why is it important? And what role can it play in addressing climate change? To find out, we talked to Columbia Climate School researchers Dorothy Peteet, Ajit Subramaniam, and Romany Webb about just some of the opportunities and challenges to working with carbon from ocean and coastal ecosystems.
Protecting and Leveraging Blue Carbon
Scientists are exploring blue carbon in two main ways. First, they want to measure and preserve the carbon that’s already stored in the oceans and coastal wetlands, such as marshes and mangrove forests. Second, they want to know how we might leverage these ecosystems to mitigate climate change.
Dorothy Peteet, a senior research scientist at NASA/Goddard Institute for Space Studies and adjunct professor at Columbia University’s Department of Earth and Environmental Sciences, is trying to solve the first riddle. She and her colleagues at Lamont-Doherty Earth Observatory are measuring the carbon content in the sediments of local marshes.
“Salt marshes store about 50 times more carbon than terrestrial forests, despite their relatively small area,” she said. “This carbon is at risk with sea level rise, and will contribute to atmospheric greenhouse gas heating if the marshes are flooded.”
Looking above the sediments, Subramaniam, a research professor and oceanographer at Columbia Climate School’s Lamont Doherty Earth Observatory, focuses on the organisms living in these ecosystems and their ability to store carbon. “There is a lot of carbon stored in the stocks, seagrasses, and microalgae in the ocean and growing along the coast. So you want to make sure that any coastal development or building or human activities, such as shrimp farming or aquaculture, don’t end up releasing this carbon,” he said.
Studies [Nature Communications (below)] have shown that wetlands store [Science (below)] between 20 and 30% of the world’s carbon, which is particularly impressive compared with the relatively small land surface they cover.

Carbon storage in biogeomorphic wetlands.
Organic carbon (A) stocks, (B) densities, and (C) sequestration rates in the world’s major carbon-storing ecosystems. Oceans hold the largest stock, peatlands (boreal, temperate, and tropical aggregated) store the largest amount per unit area, and coastal ecosystems (mangroves, salt marshes, and seagrasses aggregated) support the highest sequestration rates. (D and E) Biogeomorphic feedbacks, indicated with arrows, can be classified as productivity stimulating or decomposition limiting. Productivity-stimulating feedbacks increase resource availability and thus stimulate vegetation growth and organic matter production. Although production is lower in wetlands with decomposition-limiting feedbacks, decomposition is more strongly limited, resulting in net accumulation of organic matter. (D) In fens, organic matter accumulation from vascular plants is amplified by productivity-stimulating feedbacks. Once the peat rises above the groundwater and is large enough to remain waterlogged by retaining rainwater, the resulting bog maintains being waterlogged and acidic, resulting in strong decomposition-limiting feedbacks. (E) Vegetated coastal ecosystems generate productivity-stimulating feedbacks that enhance local production and trapping of external organic matter.
Figure 1: Map of the distribution of wetland probability sites.

Sites (black points) were sampled as part of the US Environmental Protection Agency’s 2011 National Wetland Condition Assessment (NWCA) and were analysed by five regions, Tidal Saline (blue area), Coastal Plains (green area), Eastern Mountains and Upper Midwest (purple area), Interior Plains (orange area) and West (red area).
Figure 2: Mean soil organic carbon density to a depth of 120 cm by National Wetland Condition Assessment Wetland Type for wetlands of the conterminous United States.

Carbon densities are reported as tC ha−1. National Wetland Condition Assessment (NWCA) Wetland Types include estuarine emergent (EH), estuarine woody (EW), palustrine, riverine and lacustrine emergent (PRL-EM), palustrine, riverine and lacustrine shrub (PRL-SS), palustrine, riverine and lacustrine forested (PRL-FO), palustrine, riverine and lacustrine farmed (PRL-f), palustrine, riverine and lacustrine unconsolidated bottom and aquatic bed (PRL-UBAB). The grey hatch within the bars represents the top 10 cm of the soil profile (within the 0–30 cm depth increment), followed by progressively lighter shading to represent 0–30, 30–60, 60–90 and 90–120 cm soil depths from the surface. Error bars (both white and black) represent s.e.m. Numerical values for this figure are presented in Supplementary Table 5 [in the science paper].
Figure 3: Mean soil organic carbon density to a depth of 120 cm for different subpopulations.

Carbon densities (tC ha−1) are shown for (a) the nation and in five regions, (b) tidal saline wetlands (blue) and freshwater inland (teal) wetlands and (c) least (green), intermediately (yellow) and most disturbed (red) wetlands. Wetland geographic regions include Tidal Saline (TS; coastal and estuarine), Coastal Plains (CPL), Eastern Mountains and Upper Midwest (EMU), Interior Plains (IPL) and West (W). The grey hatch within the bars represents the top 10 cm of the soil profile (within the 0–30 cm depth increment), followed by progressively lighter shading to represent 0–30, 30–60, 60–90 and 90–120 cm soil depths from the surface. Note the data shown in b,c are calculated using the data shown in a. For 0–10, 0–30, 30–60, 60–90 and 90–120 cm, respectively, the number of samples (n) for each subpopulation (identified in subscript after the n) were as follows: nnational=856, 853, 785, 590 and 435, nts=282, 282, 270, 191 and 127, ncpl=212, 211, 181, 139 and 110, nemu=137, 135, 125, 99 and 71, nipl=109, 109, 97, 71 and 57 and nw=116, 116, 112, 90 and 70. For tidal saline wetlands, n=282, 282, 270, 191 and 127 and for freshwater inland wetlands, n=574, 571, 515, 399 and 308, for 0–10, 0–30, 30–60, 60–90 and 90–120 cm, respectively. nleast disturbed=173, 172, 164, 105 and 69, nintermediately disturbed=404, 404, 363, 278 and 193 and nmost disturbed=279, 277, 258, 207 and 173 for 0–10, 0–30, 30–60, 60–90 and 90–120 cm, respectively. Error bars (both white and black) represent s.e.m. Numerical values for this figure are presented in Supplementary Table 5 [in the science paper].
Protecting the wetlands with captured carbon is vital, but we can’t stop there, Subramaniam continued, noting that the arguably more important way we think of blue carbon is with the goal of drawing carbon out of the atmosphere.
“As you go offshore, many of the proposed plans to remove carbon from the atmosphere start with growing kelp—which draws down carbon dioxide during photosynthesis—and then harvesting it. And here again, you have divergent pathways you can take: You can consume or repurpose the kelp. Or you can sink and bury it in a durable way,” he said.
Subramaniam believes repurposing kelp—in the form of food or biofuel—is not a sufficient approach to address the urgency of climate change, since the carbon would return to the atmosphere once the kelp is consumed or burned. “If you think of green biodiesel, it’s great and one more way to bend the emissions curve downward. But it’s not going to actually reduce the rate of emission or the amount of carbon in the atmosphere.” This is a first step, but “replacing diesel with biodiesel” can’t be the end goal, he said.
The other option, then, is to sink the kelp deep in the ocean for at least 100 years so that the carbon captured by photosynthesis does not go back into circulation in the atmosphere, Subramaniam said. Ideally, over the course of that century, you’ve also bought scientists and engineers time to come up with new and better technologies.
“We already have models that help us figure out how deep we need to sink the carbon and for how long it’ll stay there. But when you do this, you’re impacting a different ecosystem, which needs to be considered, too,” he said.
‘A Nature-Based Solution’
For one of his current projects, Subramaniam is proposing what he calls “a nature-based solution” for carbon removal that takes Sargassum macroalgae and sinks it down to 2,000 meters below the ocean’s surface. Sargassum is a pelagic macroalgae, which means it spends its entire lifecycle on the surface of the ocean and is visible to the eye. “It’s never attached to land and doesn’t come onshore unless it’s washed up and beached.”

Close up view of Sargassum seaweed on Crane Beach, Barbados. Photo: Clump via Creative Commons.
While this macroalgae has been recognized for centuries, in just over the last 10 or 20 years, there’s a new population growing much closer to the equator, Subramaniam said. “They call it the ‘Great Sargassum Belt,’ essentially extending from the West African coast all the way to the Mexican coast through the Gulf of Mexico in the Caribbean. It’s a major nuisance.”
This kelp is piling up on beaches in the Windward Islands of the Caribbean and devastating their economy, which is largely dependent on tourism, he added. “How do you get rid of it? You can’t bury it. You can’t take it off the beaches and put it anywhere on land because the islands are too small.”
Instead, Subramaniam and his colleagues are hoping to use advanced technology including remote sensing, artificial intelligence, and marine robotics “to drive a series of platforms that are pulling nets behind them about 15 or 20 miles offshore to capture the Sargassum before it comes to the beach.”
Once a net is full of this macroalgae, it is built to break, he explained, and when this happens, there is a fastener on the net designed to close it off. The fastener has a weight attached, which will then sink this Sargassum down to 2,000 meters, meaning “we’d be taking this carbon out of circulation completely,” he said.
“There are about 1 million metric tons of Carbon in this ‘new’ Sargassum population,” Subramaniam said. As a conservative estimate, he believes they can sink at least 10% of this carbon using the proposed technology, or about 100,000 metric tons a year. “For context, the Orca facility in Iceland, the largest carbon capture plant, has the capacity to pull 4000 metric tons per year from the atmosphere.”
Of course, one of the important points to consider when proposing a method like this one is the carbon life-cycle analysis. “You can’t expend 100 kilograms of carbon to sink 10 kilograms of carbon, for example. We need to make sure the amount of carbon we expend in sinking it is not more than the carbon we sink,” he said. They hope the use of remote sensing and robotic and artificial intelligence will maximize efficiency.
Subramaniam noted that he is personally “deeply suspicious of geoengineering,” but because the Sargassum population in question is new—and thus likely already connected to human activity and climate change—he feels comfortable with its removal.
He is also working with Webb, associate research scholar at Columbia Law School and deputy director of the Sabin Center for Climate Change Law, to look into the legal aspects of this process, since it falls within gray areas of existing environmental laws.
Legal and Social Considerations

Romany Webb researches legal issues associated with the development and deployment of negative emissions technologies on land and in the ocean.
“I think there are a lot of unanswered scientific questions about the role of blue carbon in mitigating climate change,” said Webb, who spends a lot of her time considering the techniques that remove and store carbon dioxide from the atmosphere, and the frameworks meant to ensure they occur in a safe and responsible way.
But along with the scientific questions, there are also social and governance issues that could affect whether we can make effective use of any proposed strategies, she added. “We may have social or public opposition to projects because they’re seen as being unnatural or as interfering with the ocean ecosystem, which many view as the last untouched part of the Earth, or because they’re seen as affecting other ocean-based activities. Some groups have also expressed concern that, because projects would take place in the ocean, which is part of the global commons, they may be subject to limited oversight and control by national governments.”
While a large body of international law applies to ocean-based activities, there is no comprehensive international legal framework that deals specifically with ocean carbon removal techniques, she said, leading to a lot of uncertainty. For example, ocean fertilization and ocean alkalinity enhancement, where you’re adding substances to the water, could be viewed as a form of ocean dumping, which has an established international legal framework.
“That framework, however, was developed to address things like dumping oil into oceans,” she said. Plus, as Subramaniam points out for his project, “in this case you’re taking what’s already in the ocean and moving it to a different place.”
Another challenge, Webb added, is that the closer you get to shore, the more likely there are to be domestic laws, creating potentially overlapping frameworks. “In the U.S. specifically, domestic laws can include multiple layers of government because you might have federal, state, and even local laws. So there’s a lot of complexity and uncertainty about how different activities will be treated and how they will fit into existing frameworks that were not really developed for carbon removal.”
Next Steps
Webb and her colleagues at the Sabin Center are currently working on a book that examines these existing international and national legal frameworks, and how they apply to different ocean-based carbon removal activities. In addition to studying U.S. laws, they are also working with legal academics from six other countries (China, Canada, Germany, Norway, the Netherlands, and the U.K.). The book—titled Ocean Carbon Dioxide Removal for Climate Mitigation: The Legal Framework—will be published this spring.
At the same time, Webb and her colleagues at the Sabin Center are also writing a set of model laws for ocean carbon dioxide removal projects. “We want to draft model legislation that could be enacted by Congress to create a comprehensive legal framework specific for ocean carbon dioxide removal research,” she said. The areas covered by this document would include: the scope of federal jurisdiction over ocean carbon dioxide removal projects, whether responsibility to oversee this research is entirely federal or if the states will have a role to play, which agencies should issue permissions and what factors they will need to consider in doing so, as well as what the environmental review and public consultation process should look like for research projects.
“We expect to publish a draft of the model legislation early in 2023,” Webb said.
Through initiatives like these, experts hope to bring more clarity to the growing field of blue carbon research—for scientists, lawmakers, and the general public.
Nature Communications
Science 2022
See the full article here .
Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

five-ways-keep-your-child-safe-school-shootings
Please help promote STEM in your local schools.

Stem Education Coalition

The Lamont–Doherty Earth Observatory is the scientific research center of the Columbia Climate School, and a unit of The Earth Institute at Columbia University.

It focuses on climate and earth sciences and is located on a 189-acre (64 ha) campus in Palisades, New York, 18 miles (29 km) north of Manhattan on the Hudson River.
The Lamont–Doherty Earth Observatory was established in 1949 as the Lamont Geological Observatory on the weekend estate of Thomas W. and Florence Haskell Corliss Lamont, which was donated to the university for that purpose. The Observatory’s founder and first director was Maurice “Doc” Ewing, a seismologist who is credited with advancing efforts to study the solid Earth, particularly in areas related to using sound waves to image rock and sediments beneath the ocean floor. He was also the first to collect sediment core samples from the bottom of the ocean, a common practice today that helps scientists study changes in the planet’s climate and the ocean’s thermohaline circulation.
In 1969, the Observatory was renamed Lamont–Doherty in honor of a major gift from the Henry L. and Grace Doherty Charitable Foundation; in 1993, it was renamed the Lamont–Doherty Earth Observatory in recognition of its expertise in the broad range of Earth sciences. Lamont–Doherty Earth Observatory is Columbia University’s Earth sciences research center and is a core component of the Earth Institute, a collection of academic and research units within the university that together address complex environmental issues facing the planet and its inhabitants, with particular focus on advancing scientific research to support sustainable development and the needs of the world’s poor.
The Lamont–Doherty Earth Observatory at Columbia University is one of the world’s leading research centers developing fundamental knowledge about the origin, evolution and future of the natural world. More than 300 research scientists and students study the planet from its deepest interior to the outer reaches of its atmosphere, on every continent and in every ocean. From global climate change to earthquakes, volcanoes, nonrenewable resources, environmental hazards and beyond, Observatory scientists provide a rational basis for the difficult choices facing humankind in the planet’s stewardship.
To support its research and the work of the broader scientific community, Lamont–Doherty operates the 235-foot (72 m) research vessel, the R/V Marcus Langseth, which is equipped to undertake a wide range of geological, seismological, oceanographic and biological studies.

The Columbia University Lamont-Doherty Earth Observatory R/V Marcus Langseth.
Lamont–Doherty also houses the world’s largest collection of deep-sea and ocean-sediment cores as well as many specialized research laboratories.

Columbia University was founded in 1754 as King’s College by royal charter of King George II of England. It is the oldest institution of higher learning in the state of New York and the fifth oldest in the United States.
University Mission Statement
Columbia University is one of the world’s most important centers of research and at the same time a distinctive and distinguished learning environment for undergraduates and graduate students in many scholarly and professional fields. The University recognizes the importance of its location in New York City and seeks to link its research and teaching to the vast resources of a great metropolis. It seeks to attract a diverse and international faculty and student body, to support research and teaching on global issues, and to create academic relationships with many countries and regions. It expects all areas of the University to advance knowledge and learning at the highest level and to convey the products of its efforts to the world.
Columbia University is a private Ivy League research university in New York City. Established in 1754 on the grounds of Trinity Church in Manhattan Columbia is the oldest institution of higher education in New York and the fifth-oldest institution of higher learning in the United States. It is one of nine colonial colleges founded prior to the Declaration of Independence, seven of which belong to the Ivy League. Columbia is ranked among the top universities in the world by major education publications.
Columbia was established as King’s College by royal charter from King George II of Great Britain in reaction to the founding of Princeton College. It was renamed Columbia College in 1784 following the American Revolution, and in 1787 was placed under a private board of trustees headed by former students Alexander Hamilton and John Jay. In 1896, the campus was moved to its current location in Morningside Heights and renamed Columbia University.
Columbia scientists and scholars have played an important role in scientific breakthroughs including brain-computer interface; the laser and maser; nuclear magnetic resonance; the first nuclear pile; the first nuclear fission reaction in the Americas; the first evidence for plate tectonics and continental drift; and much of the initial research and planning for the Manhattan Project during World War II. Columbia is organized into twenty schools, including four undergraduate schools and 15 graduate schools. The university’s research efforts include the Lamont–Doherty Earth Observatory, the Goddard Institute for Space Studies, and accelerator laboratories with major technology firms such as IBM. Columbia is a founding member of the Association of American Universities and was the first school in the United States to grant the M.D. degree. With over 14 million volumes, Columbia University Library is the third largest private research library in the United States.
The university’s endowment stands at $11.26 billion in 2020, among the largest of any academic institution. As of October 2020, Columbia’s alumni, faculty, and staff have included: five Founding Fathers of the United States—among them a co-author of the United States Constitution and a co-author of the Declaration of Independence; three U.S. presidents; 29 foreign heads of state; ten justices of the United States Supreme Court, one of whom currently serves; 96 Nobel laureates; five Fields Medalists; 122 National Academy of Sciences members; 53 living billionaires; eleven Olympic medalists; 33 Academy Award winners; and 125 Pulitzer Prize recipients.
Like this:
Like Loading...
Reply