Abstract
Shallow-water CO2-rich hydrothermal systems provide natural laboratories for studying localized ocean acidification under realistic environmental conditions. Here, we present a multidisciplinary characterization of the Calent mound CO2-rich system (Columbretes Islands, Western Mediterranean), based on oceanographic surveys conducted in 2020 and 2021. Localized pH anomalies were detected directly above active vents, reaching maximum reductions of 1.12 pH units, whereas water-column temperature anomalies were minimal and subsurface sediment temperatures exceeded ambient seawater by 5.67 °C. Gas analyses indicated high CO2 concentrations (0.094 ± 0.008 mol L− 1), with heterogeneous degassing regimes, ranging from sporadic to continuous emissions and an average flux of 189.4 ± 15.4 kg CO2 m− 2 yr− 1 at the active vent field. Vent fluids were significantly enriched in dissolved inorganic nutrients, particularly silicate, phosphate, nitrate+nitrite, and ammonium. Benthic microbial mats hosted metabolically diverse prokaryotic and eukaryotic communities, including hydrothermal-associated taxa such as Zetaproteobacteria, Campylobacterota, and Nitrosophaeria, consistent with iron, sulfur, and ammonia oxididation metabolisms. Several microbial core taxa persisted across years despite shifts in relative abundance. These findings demonstrate that Calent mound sustains an intense yet highly localized biogeochemical environment within the photic zone, where CO2 venting and nutrient inputs jointly influence carbonate chemistry and microbial community structure.
Acknowledgements
The authors would like to thank the officers and crew of the RV Ramón Margalef from the Spanish Institute of Oceanography (IEO-CSIC) for their invaluable help at sea. This research has been performed in the scope of the LIFE IP INTEMARES projects. LIFE IP INTEMARES project is coordinated by the Biodiversity Foundation of the Ministry for the Ecological Transition and the Demographic Challenge. It receives financial support from the European Union´s LIFE programme (LIFE15 IPE ES 012). This research was also funded by the Spanish Institute of Oceanography (IEO-CSIC) through VULCANA-II and -III (IEO-2018-2023) and ESMARES-3-VULCANA-IV (IEO-CSIC-2024-2026) projects, as well as the Promotur Turismo Canarias Agreement for the joint implementation of initiatives aimed at intelligent management and the development of the Blue Tourism product. These efforts fall within the framework of the Recovery, Transformation, and Resilience Plan (Next Generation EU Funds) and align with Order No. 257/2023 issued by the Minister of Tourism and Employment, focused on the execution of cohesion actions in destinations as part of the Canary Islands Territorial Plan. We also thank the Dirección General de Recursos Pesqueros (Secretaría General de Pesca, Ministerio de Agricultura, Pesca y Alimentación, Spain) for managing all permissions for fieldwork within the Columbretes Islands Marine Reserve (permit no. 01/20 and 01/21).
Funding
Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This research has been performed in the scope of the LIFE IP INTEMARES projects. LIFE IP INTEMARES project is coordinated by the Biodiversity Foundation of the Ministry for the Ecological Transition and the Demographic Challenge. It receives financial support from the European Union´s LIFE programme (LIFE15 IPE ES 012). This research was also funded by the Spanish Institute of Oceanography (IEO-CSIC) through VULCANA-II and -III (IEO-2018-2023) and ESMARES-3-VULCANA-IV (IEO-CSIC-2024-2026) projects, as well as the Promotur Turismo Canarias Agreement for the joint implementation of initiatives aimed at intelligent management and the development of the Blue Tourism product. These efforts fall within the framework of the Recovery, Transformation, and Resilience Plan (Next Generation EU Funds) and align with Order No. 257/2023 issued by the Minister of Tourism and Employment, focused on the execution of cohesion actions in destinations as part of the Canary Islands Territorial Plan.
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Martín-Díaz, J.P., González-Vega, A., Pérez-Barrancos, C. et al. Physical-chemical gradients, CO2 venting dynamics and microbial community composition in a shallow Mediterranean CO2-rich hydrothermal system.
Sci Rep (2026). https://doi.org/10.1038/s41598-026-57265-z
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DOI: https://doi.org/10.1038/s41598-026-57265-z
Keywords
- Shallow hydrothermal system
- Calent mound
- CO2 emissions
- PH anomaly
- Nutrient enrichment
- Microbial community.
Source: Ecology - nature.com
