Fig. 2: Sediment chronology with sedimentological parameters, sedaDNA content, information on cyanobacteria abundance and alpha diversity, and selected lake paleoenvironmental records.

Sedimentological analysis: Varve quality (where 0 = non-varved, 1 = poorly varved, and 2 = varved). Abundance of ASVs assigned to Aphanizomenon relative to total cyanobacterial ASVs (in %) based on amplicon sequencing shown for the entire Holocene (purple dots) compared to 7-methylheptadecane normalised to total organic carbon lipid biomarker shown up to ca. 6500 cal. a BP (green triangles; µg g⁻¹ TOC). Microbiological analysis: SedaDNA concentration was normalised to sediment weight (µg DNA g⁻¹ sed; magenta-coloured stars indicate metagenome-analysed samples) and to total organic carbon content (µg DNA TOC⁻¹); total cyanobacteria abundance was determined via quantitative PCR; error bars give the standard deviations for three independent amplifications; cyanobacteria taxonomic richness was retrieved from amplicon sequencing and ASV analysis. Geochemical analyses: TOC contents. Pollen-based reconstructed vegetation openness data²⁷. Dashed black lines demarcate three significantly different temporal clusters identified by non-metric multidimensional scaling (I) ca. 11,340–4070 cal. a BP, (II) ca. 3960–100 cal. a BP, and (III) ca. CE 1870–2000 (see Fig. 4). Orange-coloured sections highlight a period with phases of intensive human activities around the study site, while dark-brown grids highlight peaks in cyanobacteria abundance coinciding with warming periods.