Climate change and alien species invasions are leading to significant diversity loss and affect ecosystem functioning worldwide. In the NW Mediterranean the occurrence of unprecedented mass mortality events have been related to strong positive temperature anomalies possibly linked to climate change. On the other hand, in the Mediterranean there is an increasing number of invasive species. Up to now, most studies focus only on the effects of single disturbance source, although the potential combined effects of different disturbances are raising concern. This project will examine the direct and potential combined effects of climate change and the invasion of an algal species in the Mediterranean coralligenous. Coralligenous community is the richest one in terms of both species and organization among the Mediterranean benthic communities. It harbours great number of endangered species, long-lived organisms, very sensitive to strong disturbances. Among them, calcareous sciaphilic algae provide the structure of the community and gorgonians provide erect substrata like trees in the terrestrial forests. Gorgonians were severely affected by recent mass mortality events, but although the paramount role of calcareous algae on the structure and organization of coralligenous community we lack of quantitative information on mortality and noxious effects of positive temperature anomalies for these species. Conversely, the actual spreading of an invasive algae species may be causing strong impacts in the community and could be a major threat for the recovery process for species that have already suffered of mass mortalities due to global warming. This project will focus on 1) the factors that may favor invasion of alien species in coralligenous communities, 2) the response of calcareous algae and gorgonian populations face warming trend and invasive species. 3) the impact at a community level of positive thermal events and invasive species on coralligenous outcrops.