The process of climate change by which global temperatures increase and seasonal shifts occur is more pronounced at higher
latitudes. These changes induce shifts in the phenology of biota, including zooplankton. Regression analysis revealed signifcant advance of the spring–summer water warming in the sub-Arctic White Sea (Chupa Inlet, Kandalaksha Bay), which
occurs 3 weeks earlier in the last decade compared with 1961. The shift of timing of phenological events of Calanus glacialis,
Pseudocalanus spp., Microsetella norvegica, Oithona similis, Acartia spp., Centropages hamatus, and Temora longicornis
is particularly pronounced. These shifts were accompanied by a signifcant increase in Calanus and Microsetella abundance
with an observed decrease in Acartia abundance. No correlation between population abundance and year-to-year changes in
the species phenology was determined. We propose hypotheses to explain species adaptation to these phenological shifts in
the ecosystem: (1) fexibility of life cycle of planktonic copepods, which ensures synchronization of life cycle phases with
key events in the environment; and (2) copepod ability to switch to carnivory when algal sources are scarce. Interspecifc
interactions between ubiquitous species infuenced their phenology and abundance, while early development of Microsetella
caused later development of Oithona and higher abundance of the latter. We speculate that competition for food resources
is a driving factor in the interactions, since the trophic niches of these species overlap.