Supplemental Files Figure S1. Design of the cyanophage amendment experiment and schematic representation of the analyses conducted. Figure S2. Blast results of putative plasmids (bin.6_contog_507, bin.6_contog_750, bin.6_contog_985) identified in the genome of Nodularia spumigena. Figure S3. Elements of CRISPR-Cas systems identified in the genome of Nodularia spumigena. Figure S4. Representation of the highly compact region of cyanophage genes in the genome of Nodularia spumigena strain KAC68. Figure S5. Amino acid sequence-based phylogenetic tree reconstruction of large terminase (TerL) subunit. Blue labels indicate bacteriophages infecting various heterotrophic bacteria hosts, while green labels indicate bacteriophages infecting cyanobacteria. Cluster of cyanophages infecting Nodularia spumigena is coloured in yellow. DNA packaging mechanisms is indicated for some bacteriophages. Figure S6. Adsorption curve of the cyanophage Ravarandavirus kac68v161 to Nodularia spumigena strain KAC68 cells (a) and changes in the proportion of adsorbed cyanophages during first 6 hours post inoculation (b). Figure S7. Gene enrichments in heterotrophic bacteria comprising the microbiome of Nodularia spumigena strain KAC68. Only terms with adjusted p - values calculated using the Benjamini-Hochberg procedure (p_fdr_bh) 30Kb) in N. spumigena-associated bacteria genomes identified with PHASTEST prophage finder tool. Table S6. Predicted ORFs from the genome of Nodularia phage vB_NspS-kac68v162 (NACBI Accession No. MK605246) with identified putative homologues and functions in other organisms. Table S7. Gene enrichments in Nodularia spumigena microbiome. Table S8. Genes encoding reactions associated with riboflavin biosynthesis and metabolism identified in the genomes of heterotrophic bacteria comprising N. spumigena microbiome. Table S9. Putative horizontally transferred genes between bacteria of N. spumigena microbiome and bacterial genomes availible in the NCBI database (accessed April 2024). Table S10. Putative horizontally transferred genes within N. spumigena microbiome. Table S11. Results of PERMANOVA and db-RDA analyses comparing N. spumigena-associated bacterial consortium composition between control and different inital MOI treatments.