Marine invasions on a subtropical island: fouling studies and new records in a recent marina on Madeira Island (Eastern Atlantic Ocean)

In recent years, several marine non-indigenous species (NIS) lists have been produced for many European countries but little is known about the diversity and distribution of fouling NIS in Portugal (mainland and islands). We conducted a six-year survey of a marina located on the south coast of Madeira island, Portugal to assess NIS diversity on the island, constituting the first NIS inventory for the archipelago. We found 16 NIS, of which 9 are new records. Both species richness and abundance changed during the course of colonization whether total, NIS, or native diversity were considered. The number of native species decreased with colonization while the number of NIS significantly increased. More importantly, we demonstrated that the number of NIS detections in the marina was correlated with increasing ship traffic over the years.