Figure 5.

(a) SEM image of polished cross section of L. glaciale showing material grown under natural conditions (below the red line) and cultured under high CO₂ conditions (589 μatm, above the red line). Red line indicates the Alizarin staining. Darker areas represent smaller cells and winter growth while lighter areas represent the larger cells grown during the summer. (b) Location of the Electron microprobe analysis (EMPA, in colour) and lift outs for TEM and NanoSIMS (summer, natural environment and 596 μatm CO₂, laboratory experiments). The sample shows clear seasonal growth with lower Mg concentrations (blue colours) in wider bands and higher Mg concentrations (yellow and red colours) in the summer than in the winter.