Dietary plasticity in small Arctic copepods as revealed with prey metabarcoding

Area of Science:

• Marine Ecology
• Arctic Biology
• Food Web Dynamics

Background:

• Small copepods are vital to the Arctic marine food web.
• Their trophic interactions are poorly understood due to past methodological challenges.

Purpose of the Study:

• To investigate the diet of key small Arctic copepods: Oithona similis, Microsetella norvegica, and Microcalanus spp.
• To understand seasonal variations and species-specific differences in their prey composition.

Main Methods:

• Utilized brute force prey metabarcoding of the 18S rRNA gene.
• Analyzed samples from the Arctic Barents Sea and Nansen Basin across four seasons.

Main Results:

• Chaetognaths were the most frequent prey, comprising 47% of reads.
• Seasonal prey varied, with diatoms (43%) in April-May and dinoflagellates (15-17%) in winter.
• Microsetella norvegica showed a distinct diet compared to Oithona similis and Microcalanus spp.
• Dietary composition varied more by season than by copepod species.

Conclusions:

• Small Arctic copepods display considerable dietary plasticity, irrespective of their feeding strategies.
• This plasticity is likely an adaptation to the highly seasonal prey availability in Arctic ecosystems.