Differential response of the copepods Calanus glacialis and Pseudocalanus spp. to recent warming in the Chukchi Sea Deep Sea Research Part II: Topical Studies in Oceanography

Climate warming has impacted the Chukchi Sea resulting in reduced sea ice extent and increased water transport through the Bering Strait. This study explores the effect of recent warming by using 11 years (2010-2020) of estimated biomass data for two dominant copepods (Calanus glacialis and Pseudocalanus spp.). C. glacialis biomass declined in response to diminishing ice extent and Pseudocalanus spp. biomass increased as transport from the Bering Sea increased. Pseudocalanus spp. estimated biomass (4.61 × 108 kg) was four times greater than that of C. glacialis (1.13 × 108 kg) during the year with the lowest sea ice extent and highest transport (2019). In contrast, C. glacialis estimated biomass (1.02 × 109 kg) was 17 times greater than Pseudocalanus spp. (6.0 × 107 kg) in the year with the highest sea ice extent and lowest transport (2012). The ratio of C. glacialis biomass to total biomass decreased while the same ratio for Pseudocalanus spp. increased over time. The northern Chukchi Sea had the highest C. glacialis biomass in most years; however, significant C. glacialis biomass was observed in the southern Chukchi Sea in years with greater ice extent. During warm periods, C. glacialis biomass increased in the southern Chukchi, whereas Pseudocalanus spp. were primarily located in the southern Chukchi Sea and had equal or greater biomass than C. glacialis. Shifts in biomass towards smaller, lower lipid copepod species have the potential to impact Arctic ecosystem structure and function, specifically impacting the trophic efficiency of energy transfer in the ecosystem.