The influence of recreational boat traffic in the introduction of non-indigenous fouling species in three Ligurian marinas (Mediterranean Sea, Italy)

Abstract

The role of navigation in transporting and introducing non-indigenous species (NIS) in ports is globally acknowledged, and maritime traffic is correlated with increasing NIS introductions. On the other hand, different types of vessels can occur in a port (e.g., for commercial or recreational purposes) and the success of a NIS in a new area also depends on several chemical-physical and biotic conditions of the arrival port.In this context, a study was conducted in 2020 in three marinas at Sanremo (Ligurian Sea, Italy) with the aim to assess if boat traffic influences the presence of NIS in marine fouling communities.Samples were collected from docks and pontoons with a hand-held rigid net in the marinas of Sanremo (Porto Sole, characterized by international recreational boat traffic; and Porto Vecchio, hosting only local fishing boats), as well as in Ospedaletti, a nearly finished, abandoned and unused marina. Overall, 47 species (including 9 NIS), 45 (8 NIS) and 86 (2 NIS) were collected in Porto Sole, Porto Vecchio and Ospedaletti, respectively. Number and proportion of NIS were significantly lower in the unused marina of Ospedaletti in comparison with the other two ones, which in turn exhibited similar sessile assemblages and comparable NIS richness. The peculiarity of Ospedaletti fouling community, despite the geographical proximity and similar habitat conditions of the other marinas, highlights the role of boating traffic in facilitating NIS settlement, while the sole presence of artificial substrates is not sufficient to promote NIS introduction. This site could provide opportunities for experimenting novel NIS management measures.