MOOSE's objective is to maintain a multi-sites, integrated observation network in order to observe the effects of climate change and those induced by anthropogenic activities in the North-West Mediterranean over the long term. This SOERE- and SNO-labelled, permanent observation project, takes part in operations of the INSU's MISTRAL programme (Ocean-Atmosphere project) by ensuring LOP (Long Observing Periods) for the HYMEX, MERMEX and CHARMEX programmes, and in developing operational oceanography (MERCATOR, CORIOLIS). MOOSE's marine activities are based on a network of fixed stations (buoys, deep lines) and mobile platforms (gliders, floats) on pertinent sites set up in the North-Western Mediterranean in order to: detect and identify anomalies in the Mediterranean ecosystem over the long term, ensure lasting time series, which are the only tool for observing long-term changes, intensify the flow of real-time data to better constr ain operational oceanography models. The DYFAMED site is part of this network of fixed stations which are visited every two months in order to observe: 1) changes in the hydrological and biogeochemical properties of intermediate and deep water masses; 2) sequestration of anthropogenic carbon and acidification; and 3) the seasonal variability of the chlorophyll biomass and zooplankton communities.