DOI 10.1002/lno.11368 Arctic photoautotrophic communities must survive through polar night darkness until light returns in spring. We tracked changes in the cellular resource allocations and functional capacities of a polar sea‐ice diatom, Fragilariopsis cylindrus, to understand acclimation processes in both darkness and during the subsequent return to light. We measured parameters at specific time‐points over 3 months of darkness, and then over 6 d after a return to light. Measured parameters included cell number and size, cellular carbon and nitrogen quotas, lipid and pigment contents, concentration of key proteins of the photosynthetic system, photosynthetic parameters based on both variable fluorescence and carbon assimilation, and the level of nonphotochemical quenching. A stable functional state was reached within a few days after the transition to dark and was then maintained throughout 3 months of darkness. The dark period resulted in a decrease of lipid droplet cell quota (−6%), chlorophyll a cell quota (−41%) and the maximum carbon fixation rate per cell (−98%). Return to light after 1.5 months of darkness resulted in a strong induction of nonphotochemical quenching of excitation and a fast recovery of the maximum carbon fixation rate within 1 d, followed by a rapid increase in the cell number. Return to light after 3 months of darkness showed an increase of mortality or a profound downregulation induced over longer periods of darkness.
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Publisher's official version | 20 | 1 Mo | ||
Figure S1 Picture of the inside of the growth chamber with culture 1 (left), culture 2 (centerback) and culture 3 (right) of Fragilariopsis cylindrus grown in 20‐l polycarbonate round vessels during.. | - | 753 Ko | ||
Figure S2 Spectrum of the different light sources used during the experiments. The integral of each spectrum gives 30 μmol photons m−2 s−1. | 1 | 83 Ko | ||
Figure S3 Picture of the culture 1 (front), culture 2 (middle) and culture 3 (back) of Fragilariopsis cylindrus grown in 3‐l vessels during the Light return 1–2 experiments. Illumination of ∼30 μmol.. | - | 934 Ko | ||
Figure S4 BODIPY green fluorescence (Lipid droplet cell quota, relative fluorescence unit [RFU]) of Fragilariopsis cylindrus cultures kept in the dark at 0°C for up to 3 months and exposed to ... | 1 | 408 Ko | ||
Figure S5 a) ΦM (maximum quantum yield of PSII, dimensionless) determinations from PAM (multiple turnover technique, red) and FIRe (single turnover technique, blue) fluorometers of Fragilariopsis | 1 | 50 Ko | ||
Figure S6 a,b) Biovolume (μm3, red) and Cell number per ml (blue) c,d) Cell volume (μm3, red) and lipid droplets (RFU, blue) e,f,) μg carbon (red) and μg nitrogen per cell (blue) of Fragilariopsis ... | 1 | 55 Ko | ||
Figure S7 a) μg carbon (red) and μg nitrogen per cell (blue), b) μg carbon (red) and μg nitrogen per ml (blue) of Fragilariopsis cylindrus kept in the dark at 0°C for 3 months and exposed to ... | 1 | 46 Ko | ||
Figure S8 a,b) μg Chlorophyll a (Chla, red) and Fucoxanthin per cell (Fuco, blue) c,d) μg Diadinoxanthin (DD, red) and Diatoxanthin per cell (DT, blue) e,f) the effective absorption cross‐section for | 1 | 69 Ko | ||
Figure S9 a,b) μg PsbA (PSII protein D1, red) and μg RbcL per cell (RuBisCO large subunit, blue) b) α (initial slope of carbon fixation, [μg C cell−1 h−1 (μmol photons m−2 s−1)−1], red) and ΦM ... | 1 | 60 Ko | ||
Figure S10 a) Ek14C (Irradiance at which the carbon fixation rate saturates, μmol photons m−2 s−1, Pmax/α) and Ek PAM (Irradiance at which the electron transport rate saturates, μmol photons m−2 s−1, | 1 | 53 Ko | ||
Figure S11 a) Curves of NPQd (dynamic non‐photochemical quenching, dimensionless) of Fragilariopsis cylindrus cultures kept in the dark at 0°C for 3 months and exposed to continuous light of 30 | 1 | 97 Ko | ||
Tables S1 - S3 | 4 | 227 Ko | ||
Appendix S1: Supporting Information | 1 | 8 Ko | ||
Appendix S2: Supporting Information | 1 | 8 Ko | ||
Appendix S3: Supporting Information | 21 | 85 Ko | ||
Appendix S4: Supporting Information | 71 | 286 Ko | ||
Author's final draft | 46 | 899 Ko |
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