Fig 1.
Study region (a) Ozone depletion area for august 3, 2023 from Nasa Ozone Watch; (b) King George Island, from Arcgis; (c) Location of lake sediment coring sites at Fildes Peninsula; (d) Geographersee Lake during summer (December, 2024); Profound Lake marked by the red line Google Eart Web during (e) summer without snow (February 20, 2006); and (f) winter with snow and ice (October 19, 2005).
Fig 2.
Most abundant diatom taxa identified from the Profound Lake core.
Bar chart indicates the relative abundance of the most frequent and frequent freshwater diatoms (relative abundance above 2%) grouped into six ecological clusters (A–F) using Ward’s hierarchical clustering. In the graph on the right, the number of taxa counted per sediment layer is shown in red, and the number of valves counted is shown in gray showing the variation in abundance and diversity of taxa along the corer.
Fig 3.
Diatom microphotographs and Spearman correlations.
Inventory of the abundant diatoms detected in the sediment core and their corresponding microphotographs. Bar color represents Spearman correlations (ρ) calculated between the relative abundance of diatom taxa (derived from dated sediment layers) and the corresponding ozone concentrations at the Faraday/Vernadsky Station, Antarctica. Ozone data refer to the October ozone column concentration. Yellow boxes highlight correlations that are statistically significant within a 95% confidence interval. White bars in the microphotographs indicate scale length: 10 µm for valve views in panels (a), (d), (e), (k), (n), (o), and (p); 2 µm for lateral views in panels (b) and (f); 1 µm for valve view in panel (c); 2 µm for valve views in panels (h), (i), (j), (q), and (r); and 5 µm for valve views in panels (g), (l), (m), and (s).
Table 1.
Diatoms set and the environmental correlations.
Fig 4.
Measured and modeled ozone concentration.
Spearman correlation between modeled ozone concentrations based on the relative abundance of Gomphonema sp., Nitzschia cf. kleinteichiana, Humidophila tabellariaeformis, and Pinnularia borealis and measured October total ozone concentration at Faraday/Vernadsky Station.
Fig 5.
Ozone reconstruction model from the modern to the middleHolocene period based on diatom assemblages.
Blue line is the total ozone (DU) measured ar the Faraday/Vernadsky Station, Antarctica. The black line is ozone reconstructed based on four diatom taxa (Gomphonema sp., Humidophila tabellariaeformis, Pinnularia borealis, and Nitzschia cf. kleinteichiana) from Profound lake (left side) and Geographensee lake (right side). Bar charts refer to the relative abundance of diatoms.
Fig 6.
Ozone forcings and reconstruction models.
(a) Timeline of equivalent effective chlorine (EESC) (adapted from WMO, 2018); (b) Total Solar Irradiance (TSI) reconstruction by Krivova, Vieira and Solanki (2010) [85] (c) UV-B, 280 nm from NRLSSI2; (d) Perturbations in the mean annual optical depth (visual, λ = 0.55μm) for both hemispheres resulting from volcanic eruptions in the Southern Hemisphere adapted from Zielinski [84]; (e) confirmed volcanic eruptions data in Antarctica, obtained from the Global Volcanism Program; (f) Confirmed Global Volcanic Eruptions data, with VEI > 4 (source: Global Volcanism Program, https://volcano.si.edu/); (g) number of diatom taxa found in Profound Lake; (h) Blue line shows total ozone (DU) from Faraday/Vernadsky station, Antarctica; black line shows reconstructed ozone (this issue); (i) Ozone layer depth (DU) reconstructions, adapted from Chen et al. [86], black line shows TSI and red line the Solar Spectra Irradiance (SSI) in the 280-450nm; (j) Antarctica UVR reconstruction based on mycosporine-like amino acids as proxy [87]. Gray box highlights the period when ozone concentrations start to decrease for previously unseen values.