Passive environmental DNA (eDNA) sampling is effective for monitoring vessel biofouling in the Southern Ocean

Invasive species present a significant threat to marine ecosystems, with vessel biofouling responsible for the majority of marine invasions worldwide. The Antarctic and sub-Antarctic are some of the last regions free from known established populations of non-native marine species. Diverse biofouling communities can be transported on vessels operating in the Southern Ocean, with vessel biofouling identified as the primary vector for marine invasions in the Southern Ocean. Monitoring for non-native species in this region is challenging due to the extreme conditions and a lack of baseline biodiversity information available. We investigated the potential of passive eDNA sampling as a monitoring tool for biofouling on the icebreaking vessel MPOV Aiviq. eDNA samples were collected in the Port of Hobart, Tasmania (Australia) before, during and following in-water hull cleaning, accompanied by visual diver surveys. eDNA samples were also collected at the sub-Antarctic Macquarie Island. All eDNA samples were amplified with universal COI and 18S markers, as well as arthropod and mollusc specific markers, to gain a wide overview of taxa present. Comparison of the eDNA samples and visual surveys in Hobart provided proof of concept for the eDNA method, with known hull associated species reliably detected using eDNA. At Macquarie Island, eDNA detected 27 known hull associated taxa, including highly invasive species whose thermal range encompasses the sub-Antarctic, which could have significant impacts on native biodiversity and ecosystem function. Biofouling management for vessels operating in the Southern Ocean, with ongoing monitoring, is essential for effective biosecurity practices and to identify invasive species before they can establish.