Functional Groups of Summer Copepod Assemblage in the Central Barents Sea

The functional trait structure of copepod assemblages inhabiting Arctic seas remains poorly investigated. In the present study, we aimed to reveal the spatial pattern of copepod functional groups in the central Barents Sea. One type of water mass (the Barents Sea Water) was identified based on an analysis of water properties. Environmental gradients in oceanographic factors, nutrients, and food conditions were relatively stable. Total abundance ranged from 434 to 1168 ind. m−3, with Oithona similis dominated numerically. Total biomass ranged from 7.1 to 85.9 mg dry mass m−3, with Calanus copepods having the highest contribution. Four copepod groups were delineated based on seven key functional traits (size, trophic group, feeding mode, reproductive strategy, life cycle duration, preferred habitat, and geographic distribution). The most abundant group included Calanus finmarchicus, Pseudocalanus spp., Microcalanus spp., Centropages hamatus, and Copepoda nauplii, which attained high abundances in the northern and south-eastern sub-regions. RLQ, fourth-corner, and redundancy analyses indicated sampling depth as the most important variable explaining spatial variation in diversity, functional diversity, and copepod traits. Water temperature, chlorophyll a concentration, and nutrient levels had a significant impact on particular functional traits, including omnivore–herbivores, omnivores, cruise-feeding, mixed-feeding, long-lived, intermediate-depth dwellers, and Arctic/cosmopolitan taxa. This research provides baseline information on the functional trait structure of copepod populations in the highly productive Arctic region and can be applied to the future monitoring of pelagic assemblages.