The project EXTREMA, coordinated by IRSN, was developed in response to the ANR proposals issued in June 2006, on its program " Vulnérabilité Milieu et Climat » (VMC). The project coordinated by IRSN was developed in response to the AAP of ANR issued in June 2006 on its program "Environment and Climate Vulnerability” (VMC). The project was selected for funding by notice dated 18 April 2007 (Decision support ANR-06-Vuln-005) for an initial period of 48 months from 1 January 2007. The contract was extended for six months at the request of the consortium (August 2010) and approval of the ANR (amending Decision aid of September 29, 2010). EXTREMA was certified and supported by two clusters: The cluster "Mer PACA" oriented world and the cluster "Risk and vulnerability of territories" of regional concern. EXTREMA involved teams from the IRSN, the CEFREM (UMR 5110), the CEREGE (UMR 6635), IFREMER (Brest and Toulon Centres) and the LA (Laboratoire d’Aérologie) from the Pôle d’Océanographie Côtière de l’Observatoire Midi-Pyrénées (UMR 5560). The objectives of EXTREMA were to acquire data to record the flow of materials and contaminants during episodes of large-scale climate extremes. Data were collected across the Gulf of Lions, from the coastal river watersheds bordering the Mediterranean to the North Western submarine canyons in the middle deep margin of the continental shelf. Indeed, previous works performed by the various teams have stressed the importance of extreme events in the movement and transfer of masses in the different compartments of the biogeosphere, and the weight of these stressors in the mass balances conducted at different spatial and temporal scales (MERMEX Group, 2011). The coastal system of the Gulf of Lions was chosen because of its vulnerability to weather extremes, characterised by episodes of large amplitude (dust of Saharan origin, Rhone floods, storms), periods of dense water flows (cascading and convection), and sources of pollution (artificial radioactivity, trace metals, persistent organic compounds). The establishment and consolidation of observatories at strategic points in the Gulf of Lion has gained key information for understanding the transfer processes associated with these extreme events, and the development, validation and use of sedimentary hydro models at different scales of space and time (prodelta / Western Mediterranean basin, events / inter annual). This final report summarizes, as requested by ANR, the main significant results of the project. At the end of the project, mass transfer of contaminants associated with climate forcings or anthropogenic forcings (dam releases) were evaluated. The various inter-compartment major transfer vectors were identified. The mass dynamics of the major media acting as sinks (accumulation) and/or sources (supply) such as atmospheric dust, margins and alluvial deposits of flooding, prodeltas and deep canyons of the marine environment have been characterized. Our work has highlighted a significant change in the longer term the distribution of anthropogenic pollutants in some coastal systems may be related to the reduction of cascading and convection. A major consequence of this abrupt change would be a sequestration of pollutants at the continental shelves, privileged places of primary production and head of development of marine resources.