DNA metabarcoding captures temporal and vertical dynamics of mesozooplankton communities

In this study, we evaluated how well DNA metabarcoding of environmental samples captures changes in marine mesozooplankton community composition to optimize the use of sequencing data for studying seasonal dynamics. Although DNA metabarcoding is increasingly used to monitor the distribution of marine communities, there is a lack of standardized methods, and it remains uncertain to what extent the DNA data reflects patterns of community dynamics observed by other methods. Zooplankton net samples were collected every second week throughout 2017 in the northern Salish Sea, British Columbia. We compared metabarcoding of two genetic markers (18S targeting eukaryotes and cytochrome oxidase I targeting invertebrates) with microscopic assessments of the zooplankton collected. We also evaluated how data transformation using relative abundance, presence/absence, and the eDNA-index, affects the linearity between the morphological and genetic methods. Despite low taxonomic agreement between DNA metabarcoding and microscopy, we found most biomass dominating genera to be well represented. Using the eDNA-index, we found a generally good congruence between the seasonal cycles observed with microscopy and DNA, and that discrete water samples analyzed with DNA metabarcoding can provide information on the vertical distributions of mesozooplankton genera. We conclude by presenting guidelines for future studies that aim to use DNA to study marine zooplankton community dynamics.