Changes in the structure of marine communities and ecosystems under the influence of pollutants are evident in many Mediterranean coastal areas. An ecological survey of a polluted area can often provide more accurate and detailed information on the combined impact of pollutants than a whole range of laboratory tests and measurements. The importance and usefulness of ecological changes as indicators of the overall pollution level of certain Mediterranean areas was recognized and a research project on the effects of pollutants on marine communities and ecosystems was initiated (MED POL V) and coordinated by FAQ within the framework of MED POL Phase I.