Several species of microalgae have developed a complex specialized metabolism yielding to the production of toxic compounds. When highly concentrated and quickly multiplying, these toxic microalgae are likely to induce negative environmental or toxicological effects, by forming Harmful Algal Blooms (HABs). During the past decade, a toxic benthic dinoflagellate belonging to the genus Ostreopsis has bloomed repetitively along the Mediterranean coastline. The causes implied in the increasing incidence of these toxic blooms have not yet been determined even if global change has been pointed out. Indeed, due to its geographical features, the Mediterranean Sea is particularly sensitive to increasing temperatures and solar irradiance that would lead to enhanced thermal stratification and therefore to alterations in ecosystem functioning. Blooms of Ostreopsis were associated to human afflictions in Italy and France, such as fever, water rhinorrhea, pharyngeal pain, dry or mildly productive cough, headache, nausea/vomiting, and bronchoconstriction. Adverse effects on benthic communities of bivalves, gastropods and echinoderms were also observed in some cases. These deleterious effects on both the humans and ecosystem health were attributed to analogs of the potent palytoxin, namely ovatoxins (a to h) produced by Ostreopsis cf. ovata. However, the specialized metabolism of O. cf. ovata has been partially identified and other metabolites involved in the toxic effects are likely to be produced by the microalgae and require additional studies. Specialized metabolites are also involved in the chemical mediation between organisms and, up to now, the influence of chemical cues on the development of several benthic organisms has rarely been investigated. Therefore, any answers coming from this field named chemical ecology will be of high added value. In this context, the overall objective of OCEAN-15 is to investigate the effects of climate change on the specialized metabolism of these microalgae in order to anticipate the potential modification of its toxic behavior as well as the subsequent ecological interactions that would alter marine ecosystems. This objective fits the societal challenge 1 listed in the ANR 2015 Work Program and more specifically its axis 2 through an interdisciplinary research on "health risks facing environmental changes" bringing useful knowledge to integrative policy in public health. The project OCEAN-15 was subdivided in four main tasks addressing several aspects of the chemical ecology of O. cf. ovata: (1) study of the specialized metabolism, (2) effects of global change on this metabolism, (3) ecological impacts of the metabolism; and (4) toxicological effects and mechanisms associated to the metabolites. A truly collaborative and multidisciplinary effort will help reaching the proposed objectives. In this project, we will combine some of the leading groups in France in the field of marine chemical ecology and metabolomics (ICN), phycotoxin chemistry and ecotoxicology (IFREMER), phytoplanktonic ecology (LOV) as well as human toxicology (ANSES). The capability and success of this consortium has already been demonstrated through the joint participation of the different partners to diverse research groups supported by the CNRS (GdR Phycotox, GdR MediatEC) as well as to international consortium (ISSHA, International Society for the Study of Harmful Algae). Thus, through this synergistic project, we are convinced to bring answers on the impact of global change on Ostreopsis cf. ovata specialized metabolism and thus allelopathy and toxicity. Any answers coming from this project would benefit to the society, as they will help further monitoring of HABs and protecting human health along the touristic Mediterranean coastline.