Anthropogenic activities are one of the main drivers of the current global climate crisis. Reversing the degradation of ecosystems are strategic objectives for the 2020-2030 decade, with focused actions on the oceans due to their ability in storing CO2. Yet, the more carbon dioxide reacts with seawater, the more the pH decreases, leading to imbalances in carbonate chemistry, a process known as “ocean acidification”. Fossil skeletal archives are critical to understand and foresee the impact of climate change on oceans, providing a continuous record of past climate events. In this framework, OCEANS aims to: (i) monitor the geo-biosphere evolution on long-term and short-term scales, during periods of rapid increase of greenhouse gases resulting either in global warming or in global cooling and then warming; (ii) to examine the mechanisms which allowed the system to recover in such contrasting scenarios, triggered by the same pre-perturbation conditions we are experiencing today