Seagrass carbon stocks and fluxes in the marine and coastal protected area of Kerkennah Archipelago, East Tunisia

Author Identifier

Miguel-Angel Mateo: https://orcid.org/0000-0001-7567-0277

Oscar Serrano: https://orcid.org/0000-0002-5973-0046

Document Type

Journal Article

Publication Title

Marine Pollution Bulletin

Volume

216

Publisher

Elsevier

School

Centre for Marine Ecosystems Research / School of Science

RAS ID

81972

Funders

Gouvernement Princier, Principaute de Monaco / IUCN Mediterranean Centre for Cooperation / MEDCHANGE project funded by the Agencia Española de Investigación

Comments

Zakhama-Sraieb, R., Zribi, I., Abdelkader, N., Charfi-Cheikhrouha, F., Hmida, A. B., Sghaier, Y. R., ... & Serrano, O. (2025). Seagrass carbon stocks and fluxes in the marine and coastal protected area of Kerkennah Archipelago, East Tunisia. Marine Pollution Bulletin, 216, 118007. https://doi.org/10.1016/j.marpolbul.2025.118007

Abstract

The conservation and restoration of seagrass meadows is considered a key nature-based solution for climate change mitigation. Although Tunisia hosts more than one-third of the total extent of Posidonia oceanica meadows in the Mediterranean Sea, the lack of data on blue carbon storage in this region makes current estimates uncertain. Here, we provide the first direct estimate of biomass and soil organic and inorganic carbon stocks and accumulation rates in seagrasses P. oceanica and Cymodocea nodosa at the Kerkennah Archipelago, East Tunisia. In meadows located at water depths ranging from 1 to 3 m, P. oceanica meadows stored 156 ± 42 Mg Corg ha−1 and 673 ± 176 Mg Cinorg ha−1 in the top meter of soil, with accumulation rates of 0.36 ± 0.07 Mg Corg ha−1 yr−1 and 1.20 ± 0.33 Mg Cinorg ha−1 yr−1. The C. nodosa meadows stored 128 ± 45 Mg Corg ha−1 and 774 ± 107 Mg Cinorg ha−1 at 0.10 ± 0.04 Mg Corg ha−1 yr−1 and 0.97 ± 0.14 Mg Cinorg ha−1 yr−1 in their soils. The carbon stores in the living biomass pools of P. oceanica and C. nodosa were estimated at 17.7 ± 7.12 Mg Corg ha−1 and 1.91 ± 0.33 Mg C ha−1, respectively. The up to 2-fold higher soil Corg stocks in the seagrass compared to the adjacent unvegetated habitat confirms the role of seagrass in enhancing Corg storage. The biomass and soil Corg stocks within the 232 km2 of seagrass meadows within the planned Kerkennah Marine and Coastal Protected Area were estimated at 3.1 ± 1.1 Tg Corg. Extrapolating to the whole Tunisia, the Corg storage within the 6369–16,455 km2 of P. oceanica extent alone has been estimated at 111–286 Tg Corg sequestered at 0.23–0.59 Tg Corg yr−1. These preliminary estimates suggest that seagrasses in Tunisia sequestrate 3 to 7 % of annual emissions in the country at 2021 rates, whereas current seagrass losses at 1.74 % yr−1 result in 5 to 12 % increased annual emissions. The avoided losses of seagrass in Tunisia could have an annual 122 million € value in carbon markets at 85 € Mg CO2eq. This baseline carbon storage data provided in this study can be used towards the implementation of blue carbon conservation and restoration projects to protect seagrass carbon stores from common destructive practices in Tunisia such as illegal trawling or massive creel nets.

DOI

10.1016/j.marpolbul.2025.118007

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