Temporal succession of the major algal groups. CHEMTAX was used at the depth of the maximum chl a concentration (as indicated in mg m^–3) in the upper water column (A–I) for different expeditions. The different algal groups considered are: chlorophytes, chryso-pelagophytes, cryptophytes, diatoms, dinoflagellates, haptophytes type 7, Phaeocystis, prasinophytes type 2, and prasinophytes type 3. The depth-integrated chl a biomass over the first 100 meters (in mg m^–2) is shown by the red dots connected by dashed lines. Gray boxes indicate sea-ice concentration ≥50%. Vertical yellow dashed lines show stations for which IFCB taxonomic data were also analyzed. Note that for Resolute 2010 and 2011, only the chl a concentration at the depth of the SCM is shown (not by taxonomic groupings) in dark gray. DOI: https://doi.org/10.1525/elementa.430.f8