Deep-Sea Exploration of the US Gulf of Mexico with NOAA Ship Okeanos Explorer

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Paleolimnology in the High Arctic - implications for the exploration of Mars

Paleolimnology provides information on the past chemical, physical and biological nature of water bodies. In polar regions, where global climatic changes can be exacerbated compared with lower latitudes, the science has become important for reconstructing past changes and in so doing, predicting possible effects of future changes. Owing to the association of life with water bodies, particularly stable water bodies sustained over many millennia, paleolake regions on the surface of Mars are of exobiological importance. In this mini-review, we use experience gathered in the High Arctic to describe the importance of paleolimnology in the Earth's polar regions as it pertains to the future application of this science to robotic and human exploration missions to the planet Mar

Biosignatures associated with freshwater microbialites

Freshwater microbialites (i.e., lithifying microbial mats) are quite rare in northern latitudes of the North American continent, with two lakes (Pavilion and Kelly Lakes) of southeastern BC containing a morphological variety of such structures. We investigated Kelly Lake microbialites using carbon isotope systematics, phospholipid fatty acids (PLFAs) and quantitative PCR to obtain biosignatures associated with microbial metabolism. δC values (mean δC -4.9 ± 1.1‱, = 8) were not in isotopic equilibrium with the atmosphere; however, they do indicate C-depleted inorganic carbon into Kelly Lake. The values of carbonates on microbialite surfaces (δC) fell within the range predicted for equilibrium precipitation from ambient lake water δC (-2.2 to -5.3‱). Deep microbialites (26 m) had an enriched δC value of -0.3 ± 0.5‱, which is a signature of photoautotrophy. The deeper microbialites (>20 m) had higher biomass estimates (via PLFAs), and a greater relative abundance of cyanobacteria (measured by 16S copies via qPCR). The majority of PLFAs constituted monounsaturated and saturated PLFAs, which is consistent with gram-negative bacteria, including cyanobacteria. The central PLFA δC values were highly depleted (-9.3 to -15.7‱) relative to δC values of bulk organic matter, suggesting a predominance of photoautotrophy. A heterotrophic signature was also detected via the depleted and 15:0 lipids (-3.2 to -5.2‱). Based on our carbonate isotopic biosignatures, PLFA, and qPCR measurements, photoautotrophy is enriched in the microbialites of Kelly Lake. This photoautotrophy enrichment is consistent with the microbialites of neighboring Pavilion Lake. This indication of photoautotrophy within Kelly Lake at its deepest depths raises new insights into the limits of measurable carbonate isotopic biosignatures under light and nutrient limitations