Microbialite communities as high‐resolution archives of environmental changes: A 12,000‐yr record from Turquesa Lake, Central Andes

ABSTRACT Turquesa Lake (Central Andes) has experienced significant desiccation over the last few centuries, affecting its physico‐chemical conditions. Despite this, its stratigraphic record reveals three microbialitic levels (MI, MII, and MIII) that have colonized the lake's coast for the last ~ 12,000 yr. This offers a unique opportunity to study microbialite‐producing microorganisms' response to environmental changes, a key field in the research of the evolution of life on Earth. This study analyzes the microbiome composition of three microbialitic samples using high‐throughput DNA sequencing, lipid biomarker analysis, and scanning electron microscopy to examine microbial community structures and potential metabolic pathways. In all the microbialites, microbial communities were dominated by Proteobacteria, Planctomycetota, Firmicutes, and Cyanobacteria. Nevertheless, notable family‐level variations, particularly among eukaryotic microorganisms, were found. MII exhibited abundant green algae (Dunaliellaceae), while MIII was dominated by diatoms (Bacillariophyceae). These shifts indicate environmental changes, including a gradual increase in lake salinity from MI (oldest, lower salinity) to MIII (most recent, higher salinity). Carbon isotopic analysis (δ 13 C) revealed the Calvin–Benson–Bassham cycle as the primary carbon fixation pathway in the three microbialites, with a minor contribution from the reverse TCA cycle. The ubiquitous presence of primary producers and the prevalence of photosynthesis in the three microbialites may explain the adaptive success of these Andean microbialites despite the changing lake environment over the last 12,000 yr. In addition, the lack of change in the isotopic signature suggests that mineralogical differences in MIII were likely driven by chemical factors linked to lake desiccation and rising salinity.