Spatial variability and context-dependence of fouling communities in recreational marinas: A study in the Western Mediterranean with a focus on non-indigenous species (NIS).

Fouling communities were studied in twenty-six recreational marinas located along the continental and island coasts of Tuscany as well as Corsica (Western Mediterranean), focusing on the occurrence of non-indigenous species (NIS), in order to assess the variability of these assemblages at different spatial scales. Among the 560 taxa identified, 32 were alien or cryptogenic, with six new records for the study area. Results of this survey showed remarkable spatial variability of fouling community structure and NIS assemblage i) between marinas located on the mainland with respect to those on the islands (sectors), ii) among marinas within the same sector, and iii) among areas within the most of marinas. Macroalgae resulted the main drivers for the associated community, especially NIS, with variability level depending on different contexts. The high spatial variability observed suggests context-dependent fouling dynamics, where unique local conditions shape the structure of these communities and NIS occurrence.