Meiofauna and nematode assemblages inhabiting shallow water hydrothermal vents from the Aeolian islands

The Aeolian archipelago, located in the southern Tyrrhenian Sea harbours several shallow-water hydrothermal vents. However, the meiofauna inhabiting these systems are still largely unknown. Here, we characterized for the first time the meiofauna and nematode fauna abundance, diversity and distribution inhabiting vent areas around Vulcano and Salina Aeolian Islands in comparison with surrounding sediments. At the Vulcano and Salina islands, total meiofaunal abundance was two times higher compared to records from previous studies in the same area. The vertical distribution of meiofauna didn't show a specific pattern, either decreasing or increasing with sediment depth at different sampling points. Meiofaunal diversity didn't change significantly at increasing distance from the vent. However, significant changes in community composition were reported among sampling points and sediment layers. Nematodes represented the most abundant taxon. Nematode taxa found in proximity to the vent at Porto Levante were a subset of species that lived in background sediments but were also able to colonize and survive in extreme conditions. All trophic groups were represented underlying the ability of nematodes to use all the available food sources and/or to partition multiple food sources. Nematodes with different lifestyles (i.e., from opportunistic to intermediate colonizers, but also sensitive/persisters) were identified. Trophic composition and lifestyle are considered indices of nematode functional diversity, strongly influenced by environmental variations in physicochemical properties. The variability in the functional diversity of nematodes inhabiting Porto Levante vent site supports the important role of vent systems in sustaining a diversified nematode community covering different ecological roles.