Citizen science: a key tool for addressing knowledge gaps in the conservation status of protected species in Tuscan Mediterranean Sea

The Mediterranean Sea is a biodiversity hotspot. The heterogeneity of habitats and the great richness of species are a resource to be protected. According to the Habitats Directive (92/43/EEC), Natura 2000 network is the main instrument of the European Union for biodiversity conservation. The aim of this contribution is to apply a citizen science approach as an innovative and effective method to address knowledge gaps regarding the conservation status of six marine species in Tuscan waters (NW Mediterranean) and listed in the Habitat Directive: Centrosthephanus longispinus, Corallium rubrum, Lithophaga lithophaga, Pinna nobilis, Patella ferruginea, Scyllarides latus. This method identifies these rarest or cryptic invertebrate through well-trained citizens (divers, kayakers) whose observations (photos, videos or detailed description made by experienced observers) were validated by experts for updating Standard Forms, the identity cards of Natura (2000) sites. Results confirmed the “Endangered” C. rubrum distribution in historical sites and the presence in Tuscan archipelago of four alive specimens of “Critically Endangered” P. nobilis. For the first time the presence of P. ferruginea was recorded in a new site in Elba Island and information concerning species whose ecology is still little known as C. longispinus, L. lithophaga and S. latus, are collected. The involvement of direct observers of the marine environment makes monitoring effective and continuously updated. Information obtained may allow to propose the extension and/or the establishment of Natura (2000) sites for the safeguard of ecosystems. This innovative method can lay the basis for a temporal distribution status assessment of this species. © 2025 The Authors