Environmental DNA evidence of transfer of North Sea molluscs across tropical waters through ballast water

Abstract

Maritime transport, in particular of ballast water, is considered to be one of the most important pathways of marine biological invasions worldwide. Here we provide the first molecular evidence of potential survival of the European mudsnail, Peringia ulvae, in ballast water on cross-latitudinal voyages. Ballast water from the RV Polarstern was sampled at its departure from the North Sea and again in tropical latitudes; DNA was extracted and amplicon-sequenced employing high-throughput sequencing methodology. Mollusc species were detected by cytochrome oxidase subunit I DNA barcode sequences. The increasing proportion of operational taxonomic units that were identified as P. ulvae after 2 weeks of navigation suggests that this species withstands the harsh conditions in the ballast tank. As such, P. ulvae has the potential to reach very distant, new marine areas where it eventually might establish itself as a nonindigenous species. We also discuss the potential of environmental DNA analysis for en-route biodiversity screening and species-specific risk assessments, as well as some current limitations of the approach.