Assessing presumptive diets of Calanus copepods across stratification and productivity gradients in the Fram Strait and Barents Sea using high throughput sequencing of partial 18S PCR products from individual copepods.

An assessment of comparative feeding strategies of two Calanus groups, C. finmarchicus/glacialis and C. hyperboreus was conducted in 2016-2017 between water masses with strong gradients in productivity in the Barents Sea and the Fram Strait. DNA was extracted from individual copepods and assessed for presumptive diet through high throughput sequencing of 18S-V7 products, reducing background host signal with a blocking peptide oligonucleotide molecule. Likely diets were inferred by removing sequence reads from head-only samples. Additional bulk isotope analysis, and compound specific isotope analysis of amino acids was conducted in parallel from whole individual copepods from the same samples to determine trophic position.