Non-indigenous species contribution in the fouling communities of two recreational marinas along the Apulian coast (Ionian and South Adriatic seas)

Data on 6 months of fouling colonization on a series of panels, immersed at two different depths (0.5 m and 3 m) in two marinas along the Apulian coasts (Ionian Sea-Mar Grande of Taranto, and South Adriatic Sea-Brindisi), are reported. A total of 79 taxa were found, 59 in Taranto and 57 in Brindisi. Among them, a total of 21 NIS (non-indigenous species) were found (14 in Taranto and 19 in Brindisi), together with seven cryptogenic species (all present in Taranto and six in Brindisi). Species composition between the two sites was quite different, with only 37 species in common. By contrast, the percentage of species of each taxonomic group was quite similar, excluding the complete absence of Cnidaria in Brindisi. The best represented group was Crustacea with 24 taxa, most of which were vagile forms, followed by Polychaeta with 20 taxa, and Mollusca with only 11 taxa. Among sessile invertebrates, Tunicata and Bryozoa were represented by 15 and six taxa, respectively. Porifera and Cnidaria were poorly represented in both sites. The multivariate analysis showed the structure of the macrofouling assemblages in Taranto and Brindisi were significantly influenced by location, time and depth. Comparing the colonization pattern of the two sites, a more homogeneous situation was highlighted in Brindisi. Here, serpulids were the dominant group covering all the available substrate at both times of immersion and depths, especially after 6 months. This situation was displayed also by the MultiDimensional Scaling (MDS) analysis performed on qualitative data. The comparison of the sessile component with data relative to a previously investigated northern area (La Spezia-Ligurian Sea) revealed a different fouling assemblage with a richer community and a higher presence of NIS.