Abstract: Baseline monitoring of fouling communities in ports has unveiled the major role of navigation in the introduction and spreading of marine alien species in several geographical areas of the world. This is not the case for the Red Sea: despite the high vessel traffic in this area, ports biofouling has been poorly studied so far, leaving open questions on the pathway of bioinvasions of numerous Indo-Pacific marine species that are now occurring in the Mediterranean Sea.

In this work, a preliminary assessment on fouling communities inhabiting port habitats along the Egyptian coast of the Red Sea was carried out, with the aim to obtain baseline data and evaluate the biogeographic status of each species, considering both the Red Sea and the Mediterranean Sea (if present in the basin). Within a CICOPS fellowship, an international cooperation initiative funded by the University of Pavia (Italy), nine ports of the Egyptian coast (from Qusier to Hurghada) were surveyed for biofouling in summer 2017, by deploying PVC panels vertically, at about 1 m depth, and retrieving them after 3 months of immersion.

Taxonomic analysis, which involved a team of experts, revealed a total of about 100 taxa, out of which 77 identified at species level and classified according to their biogeographic distribution. Due to the limited knowledge of fouling communities in the Red Sea, a conservative approach in the assessment of the biogeographic status has been preferred: species with a well-documented Indo-Pacific distribution were considered ‘native’, even if not reported yet from the Red Sea (about 20 cases). Thus, the majority (60%) of the species resulted ‘native’, while only 1% could be clearly identified as ‘alien’ to the Red Sea. The remaining 39% are species with a suspect ‘cosmopolitan’ distribution, that could result either from human introduction along yet unknown trajectories (‘cryptogenic species’), or from taxonomic uncertainty (e.g., complexes of several morphologically similar species, each one being locally distributed). These species would require collaborative efforts of taxonomic and genetic analyses to solve their identity and biogeographic status.

Interestingly, half of the species observed in fouling communities inhabiting Red Sea ports are also present in the Mediterranean Sea, and 22 are considered alien in the basin, which include bryozoans, crustaceans, molluscs and polychaetes. This result supports the hypothesis that alien species entered in the Mediterranean Sea might have been introduced by vessels travelling from the Red Sea, but it does not solve the doubt whether these species are native or not to the Red Sea. For a better knowledge of fouling communities of the Red Sea and the on-going alteration of the biogeography of marine biota caused by human activities, scientific cooperation among countries for the establishment of regular monitoring programs should be promoted.