Coralligenous is a hard-bottom mainly biogenic habitat, produced by the agglomeration of calcareous encrusting algae growing in dim-light conditions. It is characterized by high structural complexity and spatial heterogeneity, thus supporting rich biodiversity and a variety of sessile assemblages, shaping a typical and one of the most important habitats of the Mediterranean Sea. It produces goods (e.g. food, raw material) and services in several domains (e.g. CO2 sequestration, aesthetics and education). Pollution, smothering and abrasion from a variety of human activities may cause its degradation at a broad scale, whilst fishing and collection of organisms mainly affect target species. Its high aesthetic value may also induce frequentation by SCUBA divers, an additional cause of degradation. Coralligenous is also susceptible to invasive alien species. This habitat, which is of great ecological, socio-economic and cultural importance, is also under the pressures linked to global warming. CIGESMED’s GOAL was to understand links between natural and anthropogenic pressures and coralligenous habitats as well as the effects on their functioning to define the Good Environmental Status (GES) of the coastal Mediterranean Sea and propose solutions for maintaining good environmental conditions. Coralligenous specific indices have been constructed and tested by scientists, marine natural parks and reserves managers, also through the implementation of a “citizen science” pilot network. The use of the newest data mining techniques and the development of visualization tools to sort, organize and illustrate very large heterogeneous sets of data constitute an original but complex approach. It permitted to mobilize, visualize and share large data collections, and to manage knowledge to study these habitats. The OUTCOME consists of: i) experimentation and results of new methods to build survey at large scales (testing operating process and materials during dive, photo analyses, population genetics, phylogenetic and metabarcoding approaches) ii) tools to diffuse new methods (website, services, training and field tools for scientists and citizen science, publications) and avoid indices misun-derstanding, iii) tools, methods and prototypes to provide datamining usable for an integrative assessment of the GES within the Framework of the Marine Strategy Directive (for this part, CIGESMED members initiated a new consortium using CIGESMED metadata and dataset to build graph representation, mine graphs and provide tools for environmental decision making). All the outcomes are freely accessible online on websites with open access, open source and open data. The overall achievement was to to bring together researchers (in ecology, economics, sociology, law, etc.) and managers in order to (i) identify the needs and to better address them, (ii) to determine interdisciplinary areas of research concerning the development and management of the coralligenous that could be the subject of a new [multidisciplinary / European / Mediterranean] research project. CIGESMED gathered scientists from France, Greece and Turkey, making it possible to assess the coralligenous habitat in a number of sites in both the northwestern Mediterranean basin and the Aegean-Levantine, under a common approach. Members of ten highly experienced marine ecology laboratories were involved. A total of 10 stations in France (in the Gulf of Lions), Greece (in the Ionian and the Aegean Seas) and Turkey (in the Aegean and the Levantine Seas) were selected to study coralligenous assemblages across the Mediterranean Sea. Analyses of photoquadrats (50x50 cm) and in situ visual observations revealed 313 species, belonging to 15 higher taxa. A total of 204 species were found in Turkey, 192 species in France and 109 species in Greece. Only fifty species were common in all sites. The abundance of the taxonomic groups in coralligenous habitats vary among sites and countries. The multivariate analysis revealed five main assemblages across the Mediterra-nean Sea. A number of important threats were withnessed to have an important impact on coralligenous, with the settlement of invasive alien species (e.g. Caulerpa cylindracea, Womersleyella setacea), sedimentation and factors causing algal bleaching being the most important ones. A new method and index were applied and tested in France (60 stations in Gulf of Lions and Provence) and Greece (4 stations in the Gulf of Corinth) to evaluate the health condition of coralligenous assemblages. This method (INDEX-COR), based on images analyses (60x40cm) and in situ observations, takes into account three metrics giving different levels of information: (i) the ratio "Sensitive-Tolerante Species", (ii) the observable taxonomic richness of the assemblages and (iii) the structural complexity. The global index combining these metrics was tested according to a global index of pressure. Reference conditions were defined in France to propose an interpretation grid to evaluate the status of coralligenous assemblages. This grid applied in Greece demonstrated the necessity to collecte multiple and complete dataset in order to define the reference conditions for the different Mediterranean sectors (e.g. Ionian Sea, Egean Sea and Cretan Sea). Finally, additional indices (CAI, COARSE and ESCA) were tested on the datasets obtained in France and Greece. The comparison of the results is still in progress. The first ones show the advantages and the limits of each index. They underline the need to achieve precisions on (i) their degree of sensitivity in the evaluation of the coralligenous assemblages and (ii) the impact of the different images analysis techniques. Although the global set of samples is still under analysis, the metabarcoding pilot study already gave very promising results for the assessment of coralligenous community species composition: many more species were identified than by eye, predicting a higher resolution than traditional approaches for monitoring and comparing coralligenous assemblages. A dedicated Citizen Science initiative was designed and launched in the course of the project, aiming to engage enthusiast divers in the study and monitoring of coralligenous assemblages through the gathering of basic information regarding spatial occurrence, assemblage structure and associated pressures and threats. The implementation platform comprises a data collection protocol and a multilingual website which serve both educational and data submission purposes. Online and paper educational documentation, as well as observation protocol guidelines are essential tools developed to train volunteer divers. Underwater slates based on the princi-ples of rapid visual assessment have also been developed and distributed to all participants for data collection. Geo-referenced data reporting focuses on: (a) basic topographic and abiotic features for the preliminary description of each site, and the creation of data series for sites receiving multiple visits; (b) presence and relative abundance of typical conspicuous species, as well as, (c) existence of pressures and imminent threats, for the characterization and assessment of coralligenous assemblages. More than 100 observation sets from across the Mediterranean have been registered to date by approximately 30 divers while 75 members have registered to the website, which remain active after the conclusion of the project. Metadata and data produced by the CIGESMED project have a high potential for use by several stakeholders involved in environmental management. Mapping this information needed to share common definitions on coralligenous components and allows starting building a micro thesaurus. The methodology is now developed and the first part of the thesaurus is online. A new consortium called IndexMed whose task is to index Mediterranean biodiversity data, makes it possible to build graphs in order to analyse the CIGESMED data and develop new solutions for coralligenous data mining. The outreach activity of the project included participation of the Consortium to an impressive number of Conferences, Symposia and Workshops, which made it possible to achieve not only the communication of the main objectives of the project but also the development of links with other projects, targeting Marine Biodiversity [e.g. EMBOS (The European Marine Biodiversity Observa-tory), LifeWatch (ESFRI Research Infrastruc-ture), DEVOTES (DEVelopment Of innovative Tools for understanding marine biodiversity and assessing good Environmental Status), VECTORS (VECTORS of Change in European Marine Ecosystems and their Environmental and Socio-Economic Impacts) and EU BON (Building the European Biodiversity Observation Net-work)]. A flyer was developed to provide the basic information on the project. The project was also advertised during much larger events, in the premises of the participating institutes, such as open days (e.g. exhibitions for the Climate change, TEDx events). The target audience for the outreach activity consisted of researchers and scientists, students, educators, environmental managers, policy makers and stakeholders from all the economic sectors including industry. The means which were used were: (a) the project website, which until now shows a high number of visits recorded for a specialized one: 250,000 hits; (b) the production of 353 articles for the scientific audience and for the society at large. Five websites have been created from which information on the project is broadcasted. The methods and datasets produced by CIGESMED are disseminated to the STIC community, as free tools for studies to be used for any type of data sciences (data mining, data representation ...), particularly through the means provided by IndexMed and through data qualification processes (which will need to be continuously improved to keep them relevant). This reusability of the data will be improved in particular by the production of data papers and future animations planned within the framework of the IndexMed consortium The Steering Committee consisting of all the WP leaders and the coordinator was responsible for all practical decision making, strategic planning and implementation. A Committee of External Advisors met at an annual basis, and aimed at providing advice on all aspects of the execution of the project to ensure CIGESMED to meet its objectives.