||Univ Perpignan, CEFREM, CNRS UMR 5110, F-66860 Perpignan, France.
IFREMER, Stn Expt Aquaculture, F-34250 Palavas Les Flots, France.
||The papers presented in this volume represent only a small part of the results obtained within the scope of the first integrated programme concerning the Mediterranean Sea. The latter is considered as a downscaled model of the ocean system, and a regional sea for the targeted projects supported by the European Commission. Whatever the domain is, the variability of the system appeared as a major feature. Consequently, this theme has been selected, among the main initial objectives, as the central subject of this volume. Spatial and temporal variabilities are considered, at different scales and at different (water, particles, sediment, trophic) levels of the marine ecosystem. In the hereafter contributions, one will find the long-term (millenar, secular and interannual), seasonal and short-term variability, the mesoscale and large-scale processes and models, including coupled ecosystem models. These results have to be considered as a significant contribution to a better understanding of the ocean as well as a base for a sustainable management of the marine systems. In effect, knowledge of the fundamental mechanisms and their variability are essential to create an efficient management of the environment. As far as the forcing functions are considered, two main factors control the variability of the Mediterranean marine system: the climate-meteorology and, directly or indirectly, the anthropogenic activity, through the use of surface waters, soils, and air. These factors have an impact on the quality (biogeochemistry) of the environment and on the dynamics, thus influencing the biological level of the system. As a result, the spatial distribution of the main wind trajectories, of runoff and rivers or straits, have a paramount influence on the observed characteristics of the various sub-basins and their gradients (north-south and west-east) over the entire basin.