Olivier SulpisScientist

Centre de recherche et d'enseignement des géosciences de l'environnement (CEREGE)1

Deep-C (Horizon Europe - ERC StG 101162777)
Deep-sea carbonates under pressure: mechanisms of dissolution and climate feedback

As humanity grapples with the escalating crisis of climate change, understanding and mitigating the sources of carbon dioxide (CO₂) emissions is imperative. A lesser-known yet significant aspect of this crisis lies in the vast expanses of marine sediments which encompass two-thirds of the Earth’s surface. A key component of these sediments is calcium carbonate (CaCO₃), a family of minerals that makes up the shells and skeletons of marine organisms. CO₂ emissions lead to ocean acidification, triggering CaCO₃ dissolution, which in turn neutralizes CO₂, acting as a crucial CO₂ sink over millennial timescales. However, the mechanisms and rate of this dissolution remain unknown due to the challenges posed by the deep ocean’s high pressures and the elusive bacterial communities mediating the dissolution process. Proposed here is an ambitious five-year research initiative aimed at understanding deep-sea CaCO₃ dissolution, thereby paving the way towards a more thorough understanding and potential mitigation of climate change impacts. By focusing on the abyssal and hadal realms, this groundbreaking research seeks to unveil the nature and rate of CaCO₃ dissolution through high pressure reactors. These reactors, which mimic the pressure and temperature of deep-sea environments, present a robust alternative to in-field studies. With the integration of cutting-edge sensors and the use of advanced CaCO₃ imaging techniques, we anticipate generating precise and continuous data on the unfolding biogeochemical processes. By housing bacterial cultures within the reactors, alongside natural CaCO₃ grains, this project will delve into the mechanisms driving dissolution. The insights will be instrumental in refining a global biogeochemical model, thereby promoting a deeper comprehension of the ocean’s role in carbon sequestration and propelling forward the global efforts towards effective climate change mitigation.

• 1Aix-Marseille Université/CNRS/IRD/INRAE