Figure 2. Sample sites in the Baltic Sea. The contour shows
averaged cold season (Feb-Apr) sea ice concentration during 2005-2015
calculated from ERA5 monthly averaged data2. The
filled circles indicate sediment samples, and the numbers show
Isochrysidales groups detected by environmental DNA and biomarkers from
sediment samples, the asterisks show predominant alkenone-producers. The
stars indicate locations where timeseries samples were collected. Note
that the Group 2 Isochrysidales found in the Baltic Sea samples were
exclusively 2i. In contrast, the Group 2 Isochrysidales found in the
Chesapeake Bay samples were exclusively 2w species (Fig.1).