DEEP-C
ERC Starting Grant (2025 -2029)
Deep-sea Carbonates under pressure: mechanisms of dissolution and climate feedbacks
The deep seafloor—one of the largest carbon reservoirs on Earth—holds immense stores of calcium carbonate (CaCO₃), a mineral critical for long-term carbon cycling and climate regulation. Human-driven ocean acidification is triggering CaCO₃ dissolution in deep-sea sediments, releasing alkalinity that helps buffer excess CO₂.
Yet, the physical and microbial controls on this process remain poorly quantified, particularly under abyssal and hadal conditions where extreme pressures prevail.
Yet, the physical and microbial controls on this process remain poorly quantified, particularly under abyssal and hadal conditions where extreme pressures prevail.
Despite its global importance for ocean biogeochemistry, CaCO₃ dissolution at depth is still modeled using outdated solubility constants and uncertain rate laws. This severely limits the reliability of Earth system models in predicting the fate of anthropogenic CO₂. Project Deep-C addresses this knowledge gap by combining high-pressure experimentation with global-scale modeling to resolve the mechanisms, rates, and climatic implications of deep-sea carbonate dissolution.
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Objectives
Deep-C aims to uncover how pressure, mineral composition, and microbial activity govern CaCO₃ dissolution in deep-sea environments.
It addresses 3 key questions:
It addresses 3 key questions:
- How does pressure influence the solubility and dissolution rate of diverse CaCO₃ minerals?
- To what extent do microbial respiration processes contribute to deep-sea CaCO₃ dissolution?
- How will changes in organic carbon flux affect global alkalinity generation and climate feedbacks?
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Approach
Deep-C uses a novel multi-scale strategy:
- High-Pressure Reactors: Custom-designed reactors will simulate abyssal to hadal pressures (up to 1000 bars) while allowing in situ monitoring of pH and oxygen. These systems will enable precise measurements of CaCO₃ solubility, molecular diffusion, and dissolution kinetics.
- Cultured and Synthetic Carbonates: 13C-labeled calcite and aragonite from cultured coccolithophores, foraminifera, algae, and synthetic minerals will be used to trace dissolution pathways under controlled conditions.
- Microbial Sediment Experiments: Sediments and microbial communities sampled off Marseille and from Japan’s hadal trenches will be used to assess how bacterial respiration influences carbonate dissolution.
- Global Modeling: Results will be integrated into the NASA-funded ECCO-Darwin ocean biogeochemical model to simulate current and future CO₂ neutralization dynamics via seafloor CaCO₃ dissolution.
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Expected Impact
Deep-C will pioneer a new generation of high-pressure oceanographic research, providing:
- Empirical rate laws and updated solubility constants for use in Earth system models
- Mechanistic insights into carbon cycling in extreme environments
- Revised estimates of CO₂ removal via deep-sea carbonate dissolution
- A pressure reactor facility at CEREGE available to the broader research community
By clarifying the role of the deep ocean in buffering anthropogenic CO₂, Deep-C will inform future climate policies and enhance predictive capacity for carbon-climate feedbacks.
Keywords
Deep sea, CaCO₃ dissolution, pressure solubility, carbon cycling, microbial respiration, high-pressure reactors, ocean alkalinity, ECCO-Darwin, foraminifera, aragonite, calcite
Deep sea, CaCO₃ dissolution, pressure solubility, carbon cycling, microbial respiration, high-pressure reactors, ocean alkalinity, ECCO-Darwin, foraminifera, aragonite, calcite
CEREGE Team
Lead
Pincipal Inverstigator :
Olivier SULPIS
sulpis@cerege.fr
Participants:
Sonia CHAABANE
Julie MEILLAND
Tom CHALK
Marine JAUMON
Maxime FELIX
Lead
Pincipal Inverstigator :
Olivier SULPIS
sulpis@cerege.fr
Participants:
Sonia CHAABANE
Julie MEILLAND
Tom CHALK
Marine JAUMON
Maxime FELIX
External Collaborators:
Christian Tamburini TAMBURINI (MIO, France)
Ronnie N.GLUD (SDU, Denmark)
Dustin CAROLL(San José State University, USA)
Christian Tamburini TAMBURINI (MIO, France)
Ronnie N.GLUD (SDU, Denmark)
Dustin CAROLL(San José State University, USA)
Project funded and hosted by :