Abstract
Blue carbon ecosystems, including mangroves and seagrasses, provide critical climate mitigation services through long-term carbon sequestration. To assess the blue carbon inventory of Mauritius, where coastal ecosystems are under increasing anthropogenic pressure, data on sediment organic carbon (OC) stocks of seagrass and mangrove ecosystems are urgently needed as they are very scarce. Extensive restoration initiatives have been implemented to recover degraded mangroves in Mauritius, but no data is available on the OC burial rate evolution along mangrove chronosequences, hindering the assessment of the success of restoration projects. This study quantified OC storage in surface sediments of seagrass habitats and age-structured restored mangroves in southern Mauritius. OC burial rates of mangroves were estimated from the temporal increase of OC in the surface sediments of stands with different ages. Seagrass meadows of Syringodium isoetifolium and Halodule uninervis stored on average 10.8 Mg C ha⁻¹, values comparable to or exceeding regional estimates from the Western Indian Ocean. Sediment parameters varied significantly among sites but showed inconsistent differences between vegetated and unvegetated habitats, highlighting strong local environmental controls. In contrast, restored Rhizophora mucronata mangroves displayed clear temporal trends: sediment dry bulk density declined linearly with stand age, while organic matter content and OC stocks increased following quadratic relationships. OC burial rates decreased with stand age to 0.58 Mg OC ha-1 year-1 at 13–17 years, about 50% of the 0–3 years rate. Old stands had fourfold higher organic matter and nearly doubled OC stocks compared to early stages, with net carbon gains of 14.3 Mg C ha⁻¹ (265.9 Mg CO₂eq ha⁻¹ for the whole restoration program). These findings contribute to the development of a comprehensive blue carbon inventory for Mauritius, highlighting the important role of seagrass ecosystems and restored mangroves in enhancing national carbon sequestration capacity. Further data collection, for example on burial rates, and improved spatial assessments are needed to robustly quantify their contribution and support their integration into national climate mitigation targets.
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Acknowledgements
The Ministry of Blue Economy, Marine Resources, Fisheries and Shipping and the PMO – Department for Continental Shelf, Maritime Zones Administration & Exploration are sincerely acknowledged for their valuable support, guidance, and collaboration throughout the course of this project. Appreciation is also extended to the project partners, namely the Association pour le Développement Durable (ADD), Attitude Foundation, and Eclosia Solidarité, for their support and contributions to the project.We thank Maria João Neves Heer for her help in the field work.
Funding
This work has been made possible through the support of the “Fonds Business Biodiversité Océan Indien” (FBBOI), administered by Expertise France under the Varuna program – Air for Biodiversity in the Indian Ocean, and funded by the Agence Française de Développement (AFD). It received Portuguese national funds from FCT – Foundation for Science and Technology through contracts UID/04326/2025, UID/PRR/04326/2025 and LA/P/0101/2020 (DOI:https://doi.org/10.54499/LA/P/0101/2020).
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Santos, R., Sunassee, S., Luchmun, D. et al. Blue carbon storage in surface sediments of seagrasses and mangroves for Mauritian inventories.
Sci Rep (2026). https://doi.org/10.1038/s41598-026-58343-y
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DOI: https://doi.org/10.1038/s41598-026-58343-y
Source: Ecology - nature.com
