Speeding up the detection of invasive bivalve species using environmental DNA: a Nanopore and Illumina sequencing comparison

Traditional detection of aquatic invasive species via morphological identification is often time- consuming and can require a high level of taxonomic expertise, leading to delayed mitigation responses. Environmental DNA (eDNA) detection approaches of multiple species using Illumina- ased sequencing technology have been used to overcome these hindrances, but sample processing is often lengthy. More recently, portable nanopore sequencing technology has become available, which has the potential to make molecular detection of invasive species more dely accessible and substantially decrease sample turnaround times. However, nanopore- sequenced reads have a much higher error rate than those produced by Illumina platforms, which s so far hindered the adoption of this technology. We provide a detailed laboratory protocol and bioinformatic tools (msi package) to increase the reliability of nanopore sequencing to detect vasive species, and we test its application using invasive bivalves while comparing it with Illumina-based sequencing. We sampled water from sites with pre-existing bivalve occurrence and abundance data, and contrasting bivalve communities, in Italy and Portugal. Samples were extracted, amplified, and sequenced by the two platforms. The mean agreement between sequencing methods was 69% and the difference between methods was non-significant. The lack detections of some species at some sites could be explained by their known low abundances. his is the first reported use of MinION to detect aquatic invasive species from eDNA samples.