Long term monitoring of Non-Indigenous Species (NIS) in the Ravenna Harbor using Autonomous Reef Monitoring Structures (ARMS)

Non-Indigenous Species (NIS) are species, introduced intentionally or unintentionally by humans outside their natural range. They can affects biological diversity, ecosystem functions and human health in the regions they invade. Owing to the departure and arrival of vessels and since the settlement of NIS can be facilitated both by the large abundance of available artificial substrates, harbours and tourist marinas are considered NIS hotspots. To adopt a standardized long-term monitoring programs is highly recommended as a preventive approach for an early identification of NIS and to obtain comparable data replicated across time and space. This study applies the ARMS program's standard protocol using an integrative approach based on ARMS deployment for three months (from April to July) in three different years (2021,2022 and 2023) in the Ravenna Harbour and a tourist Marina with a particular focus on NIS to evaluate spatial-temporal variability of the communities. The study of benthic communities was assessed by percentage coverage of the taxa trough photo analysis and vagile fauna (>2mm) was identified morphologically using a stereomicroscope and light microscope. Overall, 92 taxa belonging to 8 different Phyla were identified; 17 of them were NIS. Of these, 8 were found both in Marina and Harbour, 8 exclusively in Marina and 1 exclusively in Harbour. Harbor and Marina host significantly different benthic communities, with significantly different abundance in each year. The mean taxa richness was always significantly higher in Marina rather than in the Harbour. The differences between sites are related to their different environmental characteristic and their anthropogenic pressures. This study demonstrates that the deployment of ARMS, coupled with integrative taxonomic approaches, serves as a valuable strategy for the early detection of NIS.