In this project I will study the impact of salinity changes on the physiology of three model intertidal organisms. Organisms inhabiting the intertidal ecosystem exist in the margins of marine and terrestrial realms, and thus, must cope with dramatic physical and chemical daily changes in their environment. Understanding the physiological and evolutionary adaptations that allow these organisms to withstand such conditions will allow us to predict how further changes, in the context of climate change, will affect them. I will address this subject based on reactive oxygen (ROS) and reactive nitrogen (RNS) species production, distribution and compartmentalization, and infer on how these may play a role in the signaling and triggering of physiological defense upon environmental changes. The available information regarding this subject comes from plant physiology, and the lack of knowledge in aquatic invertebrates is significant. My experience in assessing oxidative stress and quantifying ROS/RNS production using accurate non-invasive bio-imaging techniques, and counting with the leading expertise of the host organization (ECOSYM, U. Montpellier 2) in the field of osmoregulation and salinity adaptations in invertebrates, makes the perfect team to approach this research project. The significance and relevance of this project relays on the subject being a top research priority as specified in the agenda of the ERA’s Joint Programming Initiative on Agricultural, Food security and Climate Change. Through this project I will also contribute to the technological development of tools promoted by the Competitiveness Council of the EU while consolidating my career as an independent marine ecophysiologist. I will provide novel and high impact information on the poorly known field of ROS/RNS signaling in marine invertebrates upon salinity changes which will be of key importance in understanding how intertidal invertebrates will face new changes in an already challenging environment.