Extended Data Figure 8. Scanning Electron Microscope (SEM) images of planktic foraminifer shells in Holocene sediments from Pine Island Bay.

Whole shells and detailed shell surfaces of Neogloboquadrina pachyderma sinistral morphotypes 1 and 2 from core PS75/160 are shown. Morphotype 1 (a-d) is encrusted with gametogenic calcite and dominates the upper section of the core, while thin-walled and non-encrusted morphotype 2 (e-g) dominates the lower section of core PS75/160. A scale bar (white dots) is shown in the lower right corner of each photo, and the unit of its length (number) is given in μm. Note the indistinct chambers and gametogenic calcite secreted around the whole shell in morphotype 1, while the individual chambers and porous shells of morphotype 2 are clearly visible, thereby showing beginning encrustation (white calcite around pores) (cf. refs. ^{41, 93–95}). Morphotype 1 usually dominates the lower part of the water column in Antarctic and Arctic waters and is preserved in marine sediments, whereas morphotype 2 is abundant in the upper part of the water column and not preserved in the sediments^41,93–95. Encrusted morphotype 1 is typical for the terminal life stage of N. pachyderma sin., while non-encrusted morphotype 2 is typical for its neanic (i.e. adolescent) to adult stage^41,93–96. In analogy with the SEM-defined progressive dissolution steps distinguished by Henrich⁹⁷, the shells in images a and b are affected by intermediate dissolution, the shell in image c is affected by initial to intermediate dissolution, the shell in image d is affected by initial dissolution and the shells in images e-g are well preserved.