Macrobenthic success of non-indigenous species related to substrate features in the Mar Grande of Taranto, Italy (Mediterranean Sea)

The Taranto Seas of Italy, considered a hotspot of nonindigenous species (NIS) diversity, are also among the best locales in the Mediterranean to study marine fouling communities. This environment is an ideal space to study how artificial structures are utilised by NIS for further dispersion into the surrounding environment after their initial introduction. In the present study, the fouling communities found on several types of substrates (including small artificial, mobile structures and more stable, larger structures) in a quiet enclosed part of the Mar Grande of Taranto (Ionian Sea) were analysed and compared in terms of the contribution of NIS. The assemblages differed according to the age and size of the substrate, but also according to the depth and distance from a possible source of organic enrichment. As expected, NIS were abundant, especially on small ephemeral substrates, with a high number of pioneer species; by contrast, very few NIS were found on less transient substrates, which were dominated by macroalgae. This work highlights that substrate type is an important predictor of the types of NIS present, even in environments considered to be particularly vulnerable to biological invasions, such as ports and other confined environments subject to elevated human pressure.