REduce atmospheric Carbon by Alkalinity enhancement in intertidal environments: Potential and impacts


The RECAP project intends to assess the potential benefits and risks associated with increasing alkalinity in intertidal environments, to remove carbon dioxide (CO2) from the atmosphere to combat global warming and associated environmental changes. This will be achieved by implementing an in-situ experiment, monitored continuously for 2 years, in the Ria Formosa Coastal Lagoon, in southern Portugal, using minerals rich in olivine and basalt with different grain-sizes. Monthly, water samples (supernatant and interstitial) will be analyzed for: temperature, salinity, oxygen, pH, total alkalinity, trace metals and nutrients. Quarterly, surface sediment samples will be analyzed for biodiversity composition including macrofauna, meiofauna, microfauna (benthic foraminifera), diatoms and bacteria, every three months. Statistical analyses and integration of these data will allow: 1) to constrain the effects and environmental impacts of each treatment during two seasonal cycles; 2) to depict changes between treatments and the natural environment and reveal the response of the biological community; 3) to assess the alkalinity enhancement, the metal and nutrient release for each treatment; 4) to constrain the covariation between weathering rates and climatic conditions; 5) to assess positive and negative feedbacks, in particular, the response pattern of each organism group; and 6) to identify the treatment with highest efficiency and estimate the potential sequestration of atmospheric CO2 for the entire saltmarsh area of Ria Formosa.

Project Main Goals:

To obtain strategic knowledge on the potential benefits and risks of alkalinity enhancement in intertidal environments, for future implementation of upscaling scenarios for decarbonization, contributing to define measures for mitigating climate change.


Participação no X Simpósio da Margem Ibérica Atlântica

Mendes, I., Cravo, A., Schönfeld, J., Ferreira, Ó., Carrasco, A.R., Grasse, P., Gomes, A., Correia, C., Lübbers, J., 2022. Launching project RECAP - REduce atmospheric Carbon by Alkalinity enhancement in intertidal environments: Potential and impacts. X Symposium on the Iberian Atlantic Margin Book of Abstracts, p. 74, 7-9 July, Bilbao, Spain. Book of abstracts available at:


Joachim Schoenfeld – Researcher: Helmoltz Centre for Ocean Research Kiel (GEOMAR)

Patricia Grasse – Researcher: German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig (iDiv)