Exploring intertidal sea anemones (Actinia equina) as natural eDNA samplers for coastal biodiversity assessment

Biodiversity in coastal marine environments is under unprecedented threat from anthropogenic impacts, which highlights a need for cost-effective and expedient survey methods. The analysis of environmental DNA (eDNA)—typically obtained through artificially filtered water samples—can paint a detailed picture of fish diversity in marine coastal environments. More recently, the analysis of natural sampler DNA (nsDNA, based on filter-feeding invertebrates that naturally trap eDNA in their tissues) has emerged as a potential alternative to water filtering. In this study, we investigate the widely distributed beadlet anemone Actinia equina as a potential natural eDNA sampler. Anemone samples were collected from 2 coastal locations in the UK: Rhosneigr (Anglesey, North Wales) and New Brighton (Wirral, north-western England). Sampling took place over 2 different months, and samples were compared to concomitantly sampled water. DNA metabarcoding via 12S Tele02 fish-specific primers revealed successful detection of a range of fish and other vertebrate species. We observed differences in species detected between conventional eDNA and sea anemone nsDNA samples, as well as a significant difference in seasonality detected through nsDNA. Our results indicate that the beadlet anemone can be a successful natural eDNA sampler, but that its value is more likely to reside in its complementarity alongside established eDNA methods.