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Could burying plant biomass in the oxygen-free depths of the ocean provide a viable pathway for large-scale carbon sequestration? Scientists have explored this possibility for years, and a recent international workshop led by UC Santa Barbara researchers represents an early effort to determine whether the concept could become a practical approach for long-term carbon storage.
UCSB biogeochemist Dr. Morgan Raven, a Principal Investigator at the Marine Science Institute at UC Santa Barbara, whose research focuses on organic matter in sulfidic environments, said addressing this challenge will require collaboration across disciplines and borders. She noted that the goal was to build an international network of scientists and partners to begin exploring the potential of this approach.
The workshop’s findings are published in the European Geosciences Union journal Biogeosciences.
As researchers work to address climate change driven by rising greenhouse gas emissions, reducing emissions remains essential. At the same time, scientists are investigating ways to remove carbon from the atmosphere and store it for long periods.
One emerging strategy involves sinking plant biomass into deep ocean environments where it could potentially remain stored for centuries or longer. Because plants naturally capture carbon dioxide as they grow, researchers are exploring whether placing that carbon in environments where decomposition is limited could prevent it from returning to the atmosphere.
“Plants fix an enormous amount of carbon from the atmosphere every year, naturally,” Raven explained. However, much of that carbon is typically returned to the atmosphere as the plants decay, while some of it remains locked up in wood or buried in the soil. “And so essentially the idea is that we can stop some of that carbon from going back into the atmosphere,” by sinking it to the ocean’s depths, she said.
The concept has attracted interest but has also raised concerns about potential impacts on marine ecosystems and ocean chemistry. Scientists are also studying whether carbon stored on the seafloor would remain there over long periods or eventually move back toward the surface through ocean circulation.
There’s a chance, based on what we know today, that this approach could work, if we pool the expertise of all these people from all these different fields. It’s not impossible.
Raven’s research focuses on marine anoxic carbon storage (MACS), which targets oxygen-free marine basins as potential storage sites. These environments form where circulation is restricted or where differences in water density prevent oxygen from reaching deeper waters. Their oxygen-free conditions may help preserve organic material by slowing decomposition.
Although researchers have identified anoxic basins around the world, including through previous work by Raven and her NOISE Lab, determining whether they could support carbon storage projects requires collaboration among scientists, governments, industries and local communities.
Raven emphasized that a project of this scale would require international participation and consideration of regional economic and logistical factors. She said the workshop brought together diverse perspectives, particularly from communities and nations connected to low-oxygen marine environments, so they could help shape discussions from the beginning.
Previous research identified the Black Sea as a leading candidate for MACS because of its size and isolation. Other potential locations include the Orca Basin in the Gulf of Mexico, additional brine pools and naturally occurring low-oxygen carbon storage areas associated with river deltas.
The workshop, held in Bucharest, brought together scientists, local research partners, startup representatives, policy experts, nonprofit organizations and other stakeholders. Participants evaluated potential risks, reviewed current knowledge and identified uncertainties related to storage sites, biomass sources and the carbon emissions associated with transporting material.
The resulting paper concludes that MACS may have the potential to operate at the scale needed to contribute meaningfully to climate change mitigation, a goal identified by the U.S. National Academies in 2022. The study also highlights research priorities needed before large-scale deployment can be considered, including understanding how changes in rainfall and ocean stratification could affect circulation patterns in locations such as the Black Sea.
Researchers emphasize that these questions must be answered “before we can make informed decisions about if and how to deploy MACS at scale for carbon dioxide removal.”
The collaboration remains in its early stages. While MACS could potentially contribute to addressing greenhouse gas-driven global warming, significant scientific, environmental and logistical challenges remain.
“There’s a chance, based on what we know today, that this approach could work, if we pool the expertise of all these people from all these different fields,” Raven said. “It’s not impossible.”
Adapted from original reporting by Sonia Fernandez, “UCSB-led international team evaluates anoxic marine basins as potential sites for carbon sequestration,” The Current, UC Santa Barbara, 2026.