Seagrass carbon burial: 6–15 Tg C per year from 332 cores

A team of researchers from institutions in Spain, Australia, the United States, Saudi Arabia, the United Kingdom, Denmark, Greece and Thailand has reassessed organic carbon (OC) burial in seagrass sediments. The analysis, published on 4 November 2026 in Nature Communications, is a synthesis of 332 sediment cores spanning the last century doi.org. The authors report that seagrasses bury OC at 25 ± 3 g OC m−2 yr−1 (geometric mean), with an area-weighted global average of 33 ± 9 g OC m−2 yr−1 doi.org.

Why the earlier estimates were revisited

Seagrass burial matters for coastal carbon sequestration, but global rates have remained uncertain. According to the authors, early estimates were derived from mixed methodologies across geographically and taxonomically biased datasets doi.org. The new work is presented as a data-driven reassessment of these values, built on a common synthesis of cores doi.org.

The burial rates reflect a balance between two quantities: the OC content of the sediment and the rate of sediment accumulation. The two share a negative exponential relationship, which the authors attribute to mineral dilution doi.org. Both figures above, the geometric mean and the area-weighted average, are expressed per square metre of seagrass-covered area per year doi.org.

Global burial and its share of the ocean total

The authors also revised the mapped seagrass extent, to 247,700–366,400 km2. Based on this extent, global burial scales to 6–15 Tg C yr−1 doi.org. The authors note that this is one-fourth of earlier benchmarks doi.org.

Even at the lower value, seagrasses account for 3–4% to 3–6% of total oceanic OC burial, although they cover <0.1% of the seafloor doi.org. Combined with mangroves and tidal marshes, vegetated coastal ecosystems contribute 8–13% of oceanic OC burial, according to the study doi.org.

The correspondence author is Ariane Arias-Ortiz of the Departament de Física, Universitat Autònoma de Barcelona. The co-authors are affiliated with Edith Cowan University, Florida International University, King Abdullah University of Science and Technology, Bangor University, Aarhus University and other institutions. The paper credits numerous researchers, students and technicians who created the original data sources used in the synthesis doi.org.

Seagrass meadows bury 6–15 Tg C per year, one-fourth of earlier estimates, per 332 sediment cores

Why the earlier estimates were revisited

Global burial and its share of the ocean total

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