Metabarcoding Analysis of Prey Composition of the Copepod Calanus finmarchicus in Regions of the North Atlantic Ocean

The copepod Calanus finmarchicus occupies a pivotal position in the pelagic food web of the North Atlantic Ocean. Prey choice and predator-prey dynamics at this trophic level can influence energy transfer through the ecosystem. To examine the copepod prey composition and test the hypothesis that C. finmarchicus exhibit spatial variation in diet across four basins of the North Atlantic, this study used metabarcoding analysis (high throughput sequencing of orthologous gene regions) to analyze the gut contents of C. finmarchicus. Zooplankton net samples were collected during a 2013 cruise of the R/V GO Sars in the Norwegian, Icelandic, Irminger, and Labrador basins. The V4 hypervariable region of 18S ribosomal RNA (rRNA) was used to detect a broad spectrum of potential prey items based on DNA extracted from gut contents of C. finmarchicus. Using “universal” eukaryotic primers necessitated the development of methods to limit the signal of copepod DNA relative to the DNA of its prey. Although limited in taxonomic resolution, the results provide evidence of patterns of time / space variation of major diet components of C. finmarchicus across the North Atlantic. Across the dataset, the following taxonomic groups were found in order of decreasing abundance: diatoms, dinoflagellates, cnidarians, ctenophores, apicomplexa, ciliates, nematodes, and others. Strong evidence of likely symbionts and parasites in the gut of C. finmarchicus was found. This study provides a foundation for future efforts that may utilize primers that target narrower taxonomic groups, and thereby expand the study of diet and potential prey selectivity of C. finmarchicus