A concerted action at European scale is proposed to establish the infrastructure and conditions required for marine biodiversity research. The objectives will be complemented through 3 work packages, consisting of a series of evaluations, recommendations, regional meetings and joint workshops. The CA will lead to 1) the selection and implementation of a network of Reference Sites as the basis for long-term and large-scale marine biodiversity research in Europe, 2) internationally agreed standardised and normalised measures and indicators for (the degree of) biodiversity and 3) facilities, such as a data-base, a web-site, and workshops, for further dissemination and integration of data by students, researchers, and administrators dealing with socio-economic questions, and improvement of the awareness of the public on marine biodiversity issues