Photosynthetic isotope biosignatures in laminated micro-stromatolitic and non-laminated nodules associated with modern, freshwater microbialites in Pavilion Lake, B.C.

摘要: Abstract The influence of microbial activity on carbonate precipitation was investigated within micro-stromatolitic nodules associated with modern, freshwater microbialites located in Pavilion Lake, B.C. Observed δ13C values enriched by up to + 3.6‰ as compared predicted abiotic from measured dissolved inorganic carbon (mean − 1.2‰, n = 13) were consistent photosynthetic situ the nodule microenvironment. Estimated temperatures based δ18O recorded summertime temperatures, indicative during period highest levels activity. Low organic matter (− 30.6 − 21.1‰) and an average Δδ13C value 26.8‰ reflected preferential uptake 12C non-CO2 limited photosynthesis, supporting generation 13C-enriched DIC. Microelectrode profiles through showed oxygen supersaturation ∼ 275%, elevated pH ambient water a lack any observable sulphide, Mn or Fe further indicated that predominant metabolic process light exposure. Microbial phospholipid fatty acid communities bacteria rather than eukaryotes PLFA depleted relative bulk cell 2.6–6.6‰, predominance microbes. Scanning electron microscopy images relationship between minerals filaments had occurred due influences geochemistry microenvironment surface effects trapping binding. observation photosynthetically induced 13C-enrichment precipitated is thus biosignature these hypothesized role biology formation microbialites.