Interannual and seasonal variation of the population structure,abundance, and biomass of the arctic copepod <Emphasis Type="Italic">Calanus glacialis</Emphasis> in the White Sea

The results of multiyear observations of the seasonal and inter-annual variability of the population structure, abundance, and biomass of the arctic calanoids copepod Calanus glacialis in the White Sea are presented. The spring season represents the most crucial period for the population’s seasonal dynamics. During the spring, the maximal abundance, biomass, and contribution of C. glacialis to the total zooplankton biomass is observed. The interannual variability of the abundance is closely related to the timing of the spring warming of the upper water column and the respective shifts of the onset of reproduction and the offspring development. The development of a new generation to the overwintering copepodite stage IV is usually completed three to four weeks later in the cold years compared to the warm ones. Our multiyear observations suggest that C. glacialis could be more tolerant of Arctic warming than it is usually believed. The high abundance of the C. glacialis population in the White Sea indicates that this arctic species is able to cope with the seasonal surface warming and should continue to do so, being provided with the cold water “refuge” in the deep sea.