@article {2878,
	title = {Variability in carbon uptake and (re)cycling in Antarctic cryptoendolithic microbial ecosystems demonstrated through radiocarbon analysis of organic biomarkers},
	journal = {Geobiology},
	volume = {16},
	year = {2018},
	month = {Jan-01-2018},
	pages = {62 - 79},
	abstract = {Cryptoendolithic lichens and cyanobacteria living in porous sandstone in the high-elevation McMurdo Dry Valleys are purported to be among the slowest growing organisms on Earth with cycles of death and regrowth on the order of 103{\textendash}104 years. Here, organic biomarker and radiocarbon analysis were used to better constrain ages and carbon sources of cryptoendoliths in University Valley (UV; 1,800 m.a.s.l) and neighboring Farnell Valley (FV; 1,700 m.a.s.l). Δ14C was measured for membrane component phospholipid fatty acids (PLFA) and glycolipid fatty acids, as well as for total organic carbon (TOC). PLFA concentrations indicated viable cells comprised a minor (<0.5\%) component of TOC. TOC Δ14C values ranged from -272{\textperthousand} to -185{\textperthousand} equivalent to calibrated ages of 1,100{\textendash}2,550 years old. These ages may be the result of fractional preservation of biogenic carbon and/or sudden large-scale community death and extended period(s) of inactivity prior to slow recolonization and incorporation of 14C-depleted fossil material. PLFA Δ14C values were generally more modern than the corresponding TOC and varied widely between sites; the FV PLFA Δ14C value (+40{\textperthousand}) was consistent with modern atmospheric CO2, while UV values ranged from -199{\textperthousand} to -79{\textperthousand} (calibrated ages of 1,665{\textendash}610 years). The observed variability in PLFA Δ14C depletions is hypothesized to reflect variations in the extent of fixation of modern atmospheric CO2 and the preservation and recycling of older organic carbon by the community in various stages of sandstone recolonization. PLFA profiles and microbial community compositions as determined by molecular genetic characterizations and microscopy differed between the two valleys (e.g., predominance of biomarker 18:2 [>50\%] in FV compared to UV), representing microbial communities that may reflect distinct stages of sandstone recolonization and/or environmental conditions. It is thus proposed that Dry Valley cryptoendolithic microbial communities are faster growing than previously estimated.},
	doi = {10.1111/gbi.12263},
	url = {http://doi.wiley.com/10.1111/gbi.2018.16.issue-1},
	author = {Brady, A. L. and Goordial, J. and Sun, H. J. and Whyte, L. G. and Slater, G. F.}
}
@article {513,
	title = {Photosynthetic isotope biosignatures in laminated micro-stromatolitic and non-laminated nodules associated with modern, freshwater microbialites in Pavilion Lake, BC RID B-8520-2011},
	journal = {Chemical Geology},
	volume = {274},
	year = {2010},
	note = {id: 2056; PT: J; UT: WOS:000279094700005},
	pages = {56-67},
	abstract = {The influence of microbial activity on carbonate precipitation was investigated within micro-stromatolitic nodules associated with modem, freshwater microbialites located in Pavilion Lake, B.C. Observed carbonate delta(13)C values enriched by up to +3.6 parts per thousand as compared to predicted abiotic carbonate delta(13)C values from measured dissolved inorganic carbon (mean -1.2 parts per thousand, n=13) were consistent with microbial photosynthetic influence on in situ precipitation within the nodule microenvironment. Estimated carbonate precipitation temperatures within the nodules based on delta(18)O were consistent with recorded summertime temperatures, indicative of precipitation during the period of highest levels of photosynthetic activity. Low delta(13)C values of organic matter within the nodules (-30.6 to 21.1 parts per thousand) and an average inorganic to organic carbon Delta delta(13)C value of 26.8 parts per thousand reflected the preferential uptake of (12)C during non-CO(2) limited photosynthesis, supporting the generation of (13)C-enriched DIC. Microelectrode profiles through the nodules showed oxygen supersaturation of up to similar to 275\%, elevated pH compared to ambient water and a lack of any observable dissolved sulphide, Mn or Fe further indicated that photosynthetic activity was the predominant metabolic process within the nodule during light exposure. Microbial phospholipid fatty acid profiles of the nodule communities were indicative of bacteria rather than eukaryotes and PLFA delta(13)C values were depleted relative to the bulk cell by 2.6-6.6 parts per thousand, consistent with a predominance of photosynthetic microbes. Scanning electron microscopy images of the relationship between carbonate minerals and filaments indicated that carbonate precipitation had occurred in situ due to microbial influences on the geochemistry within the nodule microenvironment rather than due to cell surface effects or trapping and binding. The observation of photosynthetically induced (13)C-enrichment of in situ precipitated carbonate within the nodule microenvironment is thus a biosignature of the activity of these surface communities and is consistent with the hypothesized role of biology in the formation of microbialites. (C) 2010 Elsevier B.V. All rights reserved.},
	issn = {0009-2541},
	doi = {10.1016/j.chemgeo.2010.03.016},
	author = {Brady, A. L. and Slater, G. F. and Omelon, C. R. and Southam, G. and Druschel, G. and Andersen, D. T. and Hawes, I. and Laval, B. and Lim, D. S. S.}
}
@article {1920,
	title = {Characterizing biodegration and microbial metabolic activity in situ using natural abundance, molecular-level 14C analysis},
	journal = {Organic Geochemistry},
	volume = {37},
	year = {2006},
	note = {id: 614},
	month = {2006},
	pages = {981-989},
	author = {Slater, G. F. and Nelson, R. K. and Kile, B. M. and Reddy, C. M.}
}
@article {1971,
	title = {Are bacteria actively degrading petroleum residues from the West Falmouth oil spill? New insights from 14C analysis of bacterial lipids},
	journal = {Environmental Science and Technology},
	volume = {39},
	year = {2005},
	note = {id: 1189},
	month = {2005},
	pages = {2552-2558},
	author = {Slater, G. F. and White, H. K. and Eglinton, T. I. and Reddy, C. M.}
}
@article {1970,
	title = {Determination of microbial carbon sources in petroleum contaminated sediments using molecular 14C analysis},
	journal = {Environmental Science and Technology},
	volume = {39},
	year = {2005},
	note = {id: 595},
	month = {2005},
	pages = {2552-2558},
	author = {Slater, G. F. and White, H. K. and Eglinton, T. I. and Reddy, C. M.}
}
@article {1969,
	title = {Determination of Microbial Carbon Sources in Petrolleum Contaminated Sediments Using Molecular 14C Analysis},
	journal = {Environ. Sci. Technol},
	volume = {39},
	year = {2005},
	note = {id: 1225},
	month = {2005},
	pages = {2552-2558},
	author = {Slater, G. F. and White, H. K. and Eglinton, T. I. and Reddy, C. M.}
}
