Sea semester samples 2020 - optimizing marine eDNA sampling at sea towards standardized marine biodiversity surveys

Samples for this project were taken in February 2020 onboard the Robert C. Seamans operating for the Sea Semester Association in Woods Hole, Massachusetts, on its leg around the Northland of New Zealand. Different combinations of sea surface sampling methods (plankton net versus a bucket sample) were assessed, two filtration setups (direct versus sequential) and two preservation strategies (DNA isolation buffer versus self-preservation filters) for metabarcoding and ddPCR analyses across three New Zealand harbors (Waitemata, Whangarei and Russell). For the tested workflows we assessed: (i) biodiversity coverage derived from the small ribosomal subunit (18S rRNA) and mitochondrial cytochrome c oxidase I (COI) genes; (ii) performance for targeted detection of the invasive Mediterranean fanworm Sabella spallanzanii via droplet digital PCR (ddPCR) assay; (iii) detection probabilities across different metazoan taxa, estimated using occupancy modelling approach. Samples were also screened for invasive species in New Zealand and their distribution patterns across the sampling stations.