The role of two non-indigenous serpulid tube worms in shaping artificial hard substrata communities: case study of a fish farm in the central Mediterranean Sea

Understanding the spread and establishment of non-indigenous species (NIS) is one of the primary areas of focus in bioinvasion science and is essential for generating appropriate management strategies in aquaculture. Here we investigated the role of 2 non-indigenous serpulid tube worms (Hydroides elegans and H. dirampha) in shaping the hard substrata communities around a fish farm in the Strait of Sicily over 1 yr (June 2014-June 2015), at 3 mo intervals (September and December 2014, March and June 2015). The mean density values of serpulids were significantly different at each sampling time. The density of serpulids on submerged panels showed a peak in spring (March 2015, after 9 mo) and decreased drastically in summer (June 2015). Hydroides shaped the entire associated macrobenthic community, which showed the highest density in the first month of observations. The lowest density was recorded in proximity to the highest density of serpulids. Margalef's species richness of the associated macrofaunal community peaked at the end of monitoring (summer). Our results will add new insights into the role of aquaculture as a vector and pathway for NIS.