Influence of artificial reefs on the surrounding infauna: analysis of meiofauna

We adopted a bottom-up approach in studying the effect of two artificial reefs in contrasting environmental conditions (sandy-mud and meso-eutrophic in the Adriatic Sea versus coarse sands and oligotrophic in the Tyrrhenian Sea) on the surrounding environment by assessing changes in the meiofauna. The spatial distribution of meiofaunal assemblages was established along a transect running from within each reef to well outside its direct sphere of influence, along with information on the trophic conditions of sediments (chloropigments, proteins, carbohydrates, and total organic matter). Although total densities were significantly higher in the Adriatic than in the Tyrrhenian, the meiofauna displayed a similar spatial distribution at the two sites, with highest densities being reached between 2 and 20 m away from the reef area and lowest densities among the reef blocks. This pattern corresponded largely with variations in grain size and oxygen penetration in the sediment. Total densities inside the reef areas were significantly lower than at the control station 50 m from the reef, suggesting that processes influencing meiofaunal assemblages largely reflect the interaction between reef and surrounding soft sediments, independently of differences in latitude, sediment texture, and trophic conditions. The results indicate that the proximity of artificial structures altered the composition of meiofaunal assemblages significantly, with potentially important implications for their role in secondary production and energy transfer to higher trophic levels.