Biodiversity monitoring of offshore structures in the Danish North Sea using environmental DNA (eDNA)

Environmental DNA (eDNA) is a cheap and accurate method for biodiversity monitoring based on sampling and analyzing the DNA that all living organisms shed to the environment. To investigate biodiversity at sites of interest in the sea, such as at and around platforms and natural reefs, it is necessary to understand the spatial and temporal variation of eDNA observations to accurately interpret and evaluate the results. Here, we used a metabarcoding approach to analyze top and bottom water samples collected along a transect from the DanF platform to Esbjerg harbor, which included both natural reefs and control stations. Temporal samples collected across 3 days using an onsite robotic sampler (ESP) were also analyzed to investigate short-term temporal variations. While general data analysis was performed using Illumina sequencing, a subset of data was further re-sequenced on the transportable ‘MinION’ sequencer from Oxford Nanopore to assess the suitability of this new technology for future on- site data generation.