Fig. 4: Diversity and enrichment analysis of marine and airborne viruses based on relative abundance in rain, snow, aerosols, sea foam, surface microlayer (SML), and subsurface water (SSW).

Alpha-diversity for all samples (except for #12, which contains 0 viruses) depicted by Shannon-Wiener index; *  = adjusted p < 0.05 (exact adjusted p = 0.0293), ****  =  adjusted p < 0.0001 in Dunn’s multiple comparison test (post hoc analysis after Kruskal-Wallis test) for rain >0.2 µm (n = 2), rain <0.2 µm (n = 2), snow (n = 1), aerosol (n = 7), sea foam (both n = 3), SML (both n = 9), and SSW (both n = 9) samples (a), non-metric multidimensional scaling (NMDS) plot based on Bray-Curtis dissimilarity (stress = 0.06) (b), and stacked bar chart on beta-diversity (c). If samples only contained rare viruses (sample #7), a single virus (#3, #5, #6, #11 #13) or no viruses (#12), they were removed, and only the relative abundance of the 200 most abundant viruses assigned to viral clusters (VCs), outliers, and singletons were considered for (b and c). In vConTACT2, outliers and singletons are unclustered and typically represent new viruses. Overlap clusters refer to genomes sharing genetic overlap with other genome(s) belonging to multiple VCs. In (c), marine samples are separated by size fraction: >0.2 µm = prokaryote fraction, <0.2 µm = viromes; Rain sample #1 is a > 0.2 µm sample, whereas #2 and #4 are rain viromes. Enrichment ratio of SML and foam viruses in rain and aerosols (d). Shown are ratios ≥1 of virus coverage for rain/foam (R/F), rain/SML (R/S), aerosol/foam (A/F), aerosol/SML (A/S), where the left tick stands for foam and SML 0.2 µm fraction and the right tick for foam and SML virome fraction in the denominator. Black fields mean that the virus was absent in one or both ecosystems in the respective sample. Grey areas show out of range fields (ratio between 0 and 1, indicating depletion). Sample number is explained in Supplementary data 12. Source data are provided as a Source Data file.