Stream water quality assessment by metabarcoding of invertebrates

Stream water quality assessments are conducted by analysing invertebrate communities as a biological quality element (BQE). In Denmark, water quality assessments of streams are often estimated according to the Danish Stream Fauna Index (DSFI). The conventional DSFI method is time consuming and requires highly specialized expertise for species identification of the relevant indicator invertebrates. Furthermore, conventional species identification of relevant indicators may be hampered by differences in, or lack of, developmental stages or due to damages during the sampling process. Metabarcoding has the potential to overcome the challenges associated with conventional morphology-based species identification. Using high-throughput DNA sequencing, metabarcoding of invertebrates collected from stream water provides an alternative to the expertise of taxonomic experts. The present study applies metabarcoding using universal invertebrate primers targeting the mitochondrial cytochrome oxidase I (COI) gene to determine stream water qualities. The obtained community profiles were compared to conventional water quality assessments according to the Danish Stream Fauna Index (DSFI). Multivariate data analysis of obtained sequences resulted in distinct clusters of taxonomic units, which reflected the stream water quality as defined by the DSFI. In conclusion, the present study supports the knowledge that invertebrates are efficient as BQE for stream water quality assessment. DNA sequencing by metabarcoding provided a unique fingerprint of the studied communities of invertebrates and was successful in describing the stream water quality.