Water sampling and eDNA preservation
In the field, seawater was collected in sterile 2 L plastic bottles
based on volumes used in previous studies in our lab and other studies
on the detection of rare and invasive species (Robson et al.2016; Simpfendorfer et al. 2016; Uthicke et al. 2018). For
all field experiments, prior to sampling, all equipment was soaked in
10% bleach for 2 hr and then rinsed with reagent-grade water (x3) to
eliminate the risk of contaminants. Equipment controls, where 500 mL of
sterilised water was passed through the water pump and filters before
placed into Longmire’s solution, were taken before sampling at each of
the sites to detect for possible cross contamination of equipment.
Environmental DNA was extracted from sea water samples using a workflow
process (Preserve, Precipitate, Lyse, Precipitate, Purify (PPLPP)),
Edmunds and Burrows, (unpublished) (Appendix S3, Supporting
information). Once precipitated through the PPLPP process, DNA was
purified using the Zymo One Step PCR Inhibitor Removal Kit (Irvine,
California, USA).