Fig 1.
TOC concentration and 13C atomic fraction of A. tepida under oxic and anoxic conditions.
(A) Average total organic carbon (TOC in μg C×ind-1) concentration and (B) 13C atomic fraction of the TOC (x(13C)TOC in %), both as a function of time. Continuous lines: oxic conditions, dotted lines: anoxic conditions. Error bars are ±1 SD (n = 3).
Fig 2.
Time-evolution of 13C uptake and transfer within the cytoplasm of A. tepida under oxic conditions.
A, D, G, J and M: TEM images; C, F, I, L and O: NanoSIMS images of corresponding 13C/12C distributions. B, E, H, K, and N: Direct correlation of TEM and NanoSIMS images. d*: Intact diatoms; d: frustules without their original contents; *: diatomic material free in the foraminiferal cytoplasm; li: lipid droplets; ol: organic lining; p: pores; r: residual bodies. Arrowheads show aperture of opened diatom frustules. Circles are drawn around a few organelles to facilitate their visualization on the different images: white circles: lipid droplets, dotted circles: residual bodies. Scale bars: 2 μm.
Fig 3.
Time-evolution of 13C uptake and transfer within the cytoplasm of A. tepida under anoxic conditions.
A, D, G, J and M: TEM images; C, F, I, L and O: NanoSIMS images of corresponding 13C/12C distributions. B, E, H, K, and N: Direct correlation of TEM and NanoSIMS images d*: Intact diatoms; d: frustules without their original contents; *: diatomic material free in the foraminiferal cytoplasm; li: lipid droplets; ol: organic lining; p: pores; r: residual bodies. Arrowheadsshow aperture of opened diatom frustules. Circles are drawn around a few organelles to facilitate their visualization on the different images: white circles: lipid droplets, dotted circles: residual bodies. Scale bars: 2 μm.
Fig 4.
Percentages of cytoplasmic occupation and 13C atomic fraction of key cell ultrastructures.
Percentage of occupation of cytoplasm area (A, C and E) and 13C atomic fraction (x(13C) in %; B, D and F) over time for key components in A. tepida: A, B: diatoms; C, D: lipid droplets; E, F: residual bodies. Errors bars are ±1 SD (n = 3).
Table 1.
Percentage of intact diatoms (frustule containing cytoplasm) in the foraminiferal cytoplasm.
Fig 5.
Relative abundances (%) of the dominant fatty acids extracted from the biofilm of diatoms and in A. tepida endoplasm.
Relative abundances (expressed in %) of the eight dominant FAs extracted from the biofilm of diatoms and in A. tepida individuals incubated under oxic (B) and anoxic (C) conditions, respectively. White: control specimens; grey: after Day 7 and black: after Day 28. Error bars are ±1 SD (n = 3).
Table 2.
Concentrations of fatty acids in A. tepida.
Table 3.
13C atomic fraction of dominant fatty acids in the cytoplasm of A. tepida.