• Alien species
• Anthropized environments
• Bionvasions
• Fouling
• Port areas

In the context of bioinvasions, ports are considered hotspots for non-indigenous species (NIS) introduction globally, due to the concentration of several invasion vectors impacting these artificial environments. Among these vectors, fouling has been identified as the major pathway involved in the introduction and spread of marine species worldwide; in particular the fouling associated to maritime traffic and ports. At global scale, the Mediterranean Sea represents one of the geographic regions most affected by the ecological process of bioinvasions. Nevertheless, the relationships between port environments, fouling and NIS are still unclear. Research topics requiring focus include how ports affect the distribution of NIS and how vectors and substrates within these environments influence the process of bioinvasion.
In order to fill these gaps, this thesis aimed at:
1. gathering the current knowledge of NIS occurrence within Mediterranean port environments;
2. describing the composition of fouling communities in Mediterranean port environments characterized by different anthropic impacts, with particular attention to the factors involved in NIS establishment;
3. assessing the influence of artificial substrate features on colonization by fouling organisms, focusing on NIS recruitment.
To accomplish these goals, one systematic review, two descriptive surveys, one correlative study and two spatio-temporal field experiments were conducted. Results of these works revealed important gaps of knowledge on NIS in Mediterranean port environments, due to the scarce comparability of studies, which were strongly taxon-focused and concentrated in specific areas of the Mediterranean Sea. In the study area (Northern Tyrrhenian Sea, Western Mediterranean), a great spatial variability of fouling communities in port environments emerged. Overall, large ports showed the highest abundance of NIS and, within them, the touristic areas exhibited a proportion of these species higher than that present in commercial ones. On the other hand, fouling communities of marinas showed a much more variable pattern among different sites, also in terms of NIS assemblages. Interestingly, a marked distinction was detected between fouling communities of marinas located on continent coasts and those located on islands. Furthermore, the occurrence of NIS within the study area was related to the abundance of highly structured sessile organisms, such as arborescent bryozoans and serpulid polychaetes. The influence of substrate morphological complexity in facilitating the establishment of NIS was supported by the high degree of colonization of these species on more complex substrates within the port of Livorno, especially in the touristic harbour. Finally, the high colonization capability of fouling NIS was underlined by their occurrence on mid-water artificial substrates, such as bare submerged mooring lines, already at early stages of colonization.
All these findings led to the hypothesis that specific combinations of abiotic features of ports (e.g topographic arrangement, water circulation, kind and intensity of maritime traffic) shape different fouling communities, characterized by different occurrences of NIS. In this context, touristic harbour of large ports emerged as a suitable area for NIS establishment, due to the marked presence of highly structured basibionts. This large amount of sessile suspension feeders could be linked to the high levels of organic pollution of water column, possibly related to the complex topographic design of these areas, that influence the water exchange. However, further investigations are needed to validate this model.
Results of this work, combined with future studies on the topic, will provide an important contribution to better understand the mechanisms of bioinvasions in anthropized environments, and will allow to design focused management plans (prevention, containment and/or mitigation) to face this growing ecological issue.