DISCUSSION
Our focus on well characterised macrobenthic communities from the North sea allowed to investigate and understand the biases inherent to DNA metabarcoding when characterising macrobenthic diversity. We found considerable differences in alpha and beta diversity patterns between the tested primer sets and between the two sample types (bulk DNA vs eDNA from the ethanol preservative) and show that the detection of macrobenthic species in the eDNA of the ethanol preservative is linked to their body size and body skeleton. In addition, the one to one comparison between morphology based identification and DNA metabarcoding of bulk DNA and eDNA from the ethanol preservative and the availability of a nearly complete reference database shows that discrepancies between morpho-taxonomic and DNA metabarcode datasets are not entirely the result of incomplete reference databases.