Effects of environmental conditions on the biomass of Calanus spp. in the Nordic Seas

The biomass of Calanus spp. in the Norwegian Atlantic Current and the West Spitsbergen Current (2001–2009) was statistically related to a combination of salinity, temperature, water depth and sea ice concentration. The aim of this study was to identify the significance of these environmental factors for controlling the species-specific biomass distribution and the nature of such relationships. Calanus finmarchicus dominated the entire area and its biomass was mainly related to salinity. Calanus glacialis was mainly found along the northwest shelf of the Barents Sea, but its biomass was also related to the sea ice concentration and temperature with a critical threshold ∼6°C, above which the presence and biomass of C. glacialis decreased. The Calanus hyperboreus biomass was related to all environmental factors, which characterized by a confined spatial distribution to water associated with the Greenland Sea Gyre. We conclude that C. hyperboreus is an expatriate to the study area. The Calanus biomass distribution will not change greatly in the study area with an expected increase of water temperature by 2°C, whereas the critical temperature threshold for C. glacialis will be exceeded with temperature increases of ∼4°C with a likely disappearance of this cold water species from the north-west shelf of the Barents Sea.