Towards quantitative metabarcoding of eukaryotic plankton: an approach to improve 18S rRNA gene copy number bias

Plankton metabarcoding is increasingly implemented in marine ecosystem assessments and more cost-efficient less time-consuming than monitoring based on microscopy (morphological). 18S rRNA gene the most widely used marker for groups’ species’ detection classification within eukaryotic microorganisms. These datasets have commonly relied acquisition of organismal abundances directly from number DNA sequences (i.e. reads). Besides inherent technical biases metabarcoding, largely varying copy numbers (GCN) among protists (ranging tens to thousands) one important biological species quantification. In this work, we present a correction factor (CF) four planktonic groups: Bacillariophyta, Dinoflagellata, Ciliophora miscellaneous flagellated cells. On basis theoretical assumption that ‘1 read’ equivalent GCN’, GCN median values per plankton group calculate corrected cell biomass relative abundances. The species-specific absolute were obtained various studies published literature. We contributed development database proposed by previous authors. To assess efficiency compared morphological (in biomass) 15 surface water samples collected Belgian Coastal Zone. Results showed application over results enables us significantly improve estimates cells, but not Bacillariophyta. This likely due large biovolume plasticity diatoms corresponding genome size numbers. C-biomass abundance estimations amplicon reads only improved Dinoflagellata Ciliophora. method still facing related low assessed. Nevertheless, increase may lead refinement factor.