Samples of benthic microbial mat, surface water carbonate films, abiotic microcosm precipitate, and abiotic control with NaOH from the laboratory experiment were analyzed by X-ray powdiffractiontion.
In the natural environment, significant isotopic differences exist between abiotically formed nesquehonite (δ13C avg. = 9.3‰, δ18O avg. = 24.9‰) and carbonates present in benthic microbial mat (δ13C avg. = 6.7‰, δ18O avg. = 17.2‰).
Samples of benthic microbial mats, surface water carbonate films, and experimental biofilms and precipitates were examined.
To determine the mineralogy (by XRD) and stable isotope compositions, samples of mineralized microbial mat, mineral films on surface waters (Fig. 1B), and carbonate crusts on exposed surfaces were collected in 50 ml plastic vials.
The plan for Alvin Dive 4636 was ambitious: deploy four experiments and collect eight authigenic carbonates, four Niskin bottles of water, 24 tube cores of seep sediment, one scoop of clams, and two "slurps" of microbial mat.
Tice, M. M. Environmental controls on photosynthetic microbial mat distribution and morphogenesis on a 3.42 Ga clastic-starved platform.
Kato, K. et al. Microbial Mat Boundaries between chemolithotrophs and phototrophs in geothermal hot spring effluents.
To our astonishment it had a completely different type of microbial mat growing at its bottom.
In modern examples, bubbles become silicified along with the microbial mat and either become infilled with sinter/microbial filaments or remain open16.
Cyclopropyl fatty acids appeared only in the microbial mat samples, consistent with their association with anaerobic bacteria33,34,37.
