Scanning ferry routes: looking for eDNA traces of marine mammals and their preys

Marine environmental DNA (eDNA) surveys are becoming a promising approach to monitor biodiversity status and its variation over time. However, monitoring offshore areas could be extremely costly when using dedicated vessels, beside the impossibility sample simultaneously geographically distant (even if adjacent) areas. The unexplored possibility of availing on operating ferries as an opportunistic platform for eDNA sampling offers several advantages besides opening limitless opportunities systematic marine biodiversity.We present results both metabarcoding barcoding approaches obtained from analysis water samples collected board ferry boat along pilot Mediterranean route crossing Pelagos Sanctuary Mammals. recently described MarVer primer sets (12SrDNA 16SrDNA regions), specifically designed simultaneous detection mammals other vertebrates, were employed. High Throughput Sequencing (HTS) outcome showed that markers successfully detected most trophic levels vertebrate communities, classes, including bony fish, rays, cetaceans birds. Ferry-based allow collect at any time day, we indeed found diel differences in quantitative qualitative distribution read counts. For instances, observed increased abundance lantern fish amplicons night-time (50%), reflecting nocturnal migration through column. In general, number counts was significantly higher samples. Such within our indirectly provides evidence efficiency detect contemporary signals sampled environment. Similarly, correspondence visual sightings (when these occurred, supplementary collected). Rare species, such monk seal, difficult surveys, thus opted side screening ferry-samples with panel species-specific qPCR assays, which able traces endangered pinniped Tuscany archipelago (Tyrrhenian Sea) long before observations witnessed presence same area. study demonstrates feasibility commercial shipping without survey cruises. Commercial routes have potential act regular transects can contribute evaluating biodiversity.