Anthropogenic CO2 emissions are absorbed by the world’s oceans, leading to decreasing marine pH and carbonate levels, a process known as ocean acidification (OA) that is threatening marine ecosystems. OASYS proposes to address critical gaps in knowledge and shortcomings of previous OA research by investigating the life-traits and sensory responses of 3 temperate marine species presenting different sensibilities to OA i.e., a demersal fish (European seabass Dicentrarchus labrax), a bivalve (Pacific oyster Crassostrea gigas) and a gastropod (European abalone Haliotis tuberculata L.). We will expose the animals to PCO2 conditions corresponding to present-day (pH 8.1) and a high CO2 emission scenario predicted for 2100 (pH 7.6) and to evaluate the impacts of OA on physiology (e.g. growth, calcification, reproduction), ecologically-relevant behaviours (e.g. feeding behavior, predator-prey interaction, settlement behaviour), and sensory capacities. In addition, OASYS will shed light on understanding the inter-generational dimension of OA by examining whether genitor acclimation to high PCO2 affects offspring phenotypes. Lastly, OASYS represents an integrative and multi-approaches project that will consider the impacts of OA on physiology, sensory performance and behaviour of temperate marine organisms at different organizational levels (gene, organ, organism) and life stages (larvae, juvenile, adult). Altogether, OASYS will evaluate the possible effects of OA on individual fitness and ultimately, on the alteration of ecosystem dynamics and structure, which would potentially impact ecosystem services.