DNA metabarcoding for high-throughput monitoring of estuarine macrobenthic communities

Benthic communities are key components of aquatic ecosystems’ biomonitoring. However, morphology-based species identifications remain a low-throughput, and sometimes ambiguous, approach. Despite metabarcoding methodologies have been applied for above-species taxa inventories in marine meiofaunal communities, a comprehensive approach providing species-level identifications for estuarine macrobenthic communities is still lacking. Here we report a combination of experimental and field studies demonstrating the aptitude of COI metabarcoding to provide robust species-level identifications within a framework of high-throughput monitoring of estuarine macrobenthic communities. To investigate the ability to recover DNA barcodes from all species present in a bulk DNA extract, we assembled 3 phylogenetically diverse communities, using 4 different primer pairs to generate PCR products of the COI barcode region. Between 78 and 83% of the species in the tested communities were recovered through HTS. Subsequently, we compared morphology and metabarcoding-based approaches to determine the species composition from four distinct sites of an estuary. Our results indicate that the species richness would be considerably underestimated if only morphological methods were used. Although further refinement is required for improving the efficiency and output of this approach, here we show the great aptitude of COI metabarcoding to provide high quality and auditable species identifications in macrobenthos monitoring.