Seagrasses are an important component of the structure and functioning of coastal ecosystems and provide essential ecological services. Seagrasses are benthic primary producers and their dependence from light determines that they inhabit shallow bottoms and therefore they are prone to be disturbed by human activities in the coastal zone. Seagrass meadows are in worldwide regression and this global trend renews the interest of research on restoration ecology, part of the ecological science that provides theoretical and practical knowledge in support of ecological restoration, the process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed. Knowledge and experience accumulated in this area show that restoration of seagrass meadows is feasible at small spatial scales but very expensive. The use of seagrass seeds or seedlings in restoration is advantageous compared to the use of fragments of adult plants. Posidonia oceanica is an endemic Mediterranean seagrass that performs essential functions in the coastal ecosystem and that is threatened by several disturbances and by its low capacity to recover from them. The local scale of many of those disturbances leads to consider ecological restoration as a sound option to facilitate the recovery of damaged meadows. Seedlings are a key stage of the life cycle of this species because they are the cores to form new meadows. Elucidating the factors that influence the survivorship and vegetative development of seagrass seedlings is fundamental to understand the dynamics of formation of new meadows and to inform the restoration process of damaged meadows. This project will evaluate the influence that the availability of light and nutrients, and herbivory have on survivorship and vegetative development of P. oceanica seedlings. These factors are highly influential on the structure and functioning of adult plants but their effects on seedlings and, consequently, on the process of formation of new meadows are unknown. The objectives of the project are 1) to characterize the photosynthetic activity of P. oceanica seeds and to evaluate its geographical and depth-related variability, 2) to determine if there is a relationship between the photosynthetic activity of the seed and the vegetative development achieved by the seedling originated from it, 3) to evaluate the potential influence that herbivory might have on the survivorship and vegetative development of seedlings, 4) to quantify the in situ herbivore pressure on seedlings, 5) to elucidate the influence that nutrient availability and herbivory might have on the in situ survivorship and vegetative development of seedlings, and 6) to integrate the results obtained to improve the technologies of P. oceanica restoration using seedlings. The methodological approach involves the production of seedlings from beach-cast fruits and their use in experiments both in the laboratory and in situ (transplants at sea).