Abstract
Environmental impact assessment and regular environmental monitoring are prerequisites for the construction, operation, and decommissioning of offshore wind farms (OWFs). Molecular approaches are increasingly being considered as a possible complement or alternative to currently used marine baseline and monitoring methods, both for water column and seafloor organism studies. The following report shows the results of a study where two molecular environmental DNA (eDNA) methods – metabarcoding and ddPCR quantitative assays – have been used to characterize the water column at the Hywind Tampen floating OWF (FOWF) based on filtered 20 m and bottom water samples from within, upstream, and downstream from the FOWF as well as three reference stations further away from the FOWF. The aim of this study was to gain further information on the performance of eDNA water samples as a method to monitor impact on the pelagic ecosystem. More specifically, this work builds upon a similar study at the Hywind Scotland Pilot Park in 2021 (Ray et al., 2022), aiming to address gaps identified in that study such as temporal stability of the results, eDNA degradation and current transport in the water through sampling the same stations at three different times. Metabarcoding was employed for a community view of a) fish fauna specifically, using the MiFish primer set, and b) a universal eukaryote dataset based on 18S V1-V2 primers. Quantitative assays were employed for two commercially important pelagic fish species: mackerel and herring.