@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 {346,
	title = {Constraining carbon sources and growth rates of freshwater microbialites in Pavilion Lake using 14C analysis},
	journal = {Geobiology},
	volume = {7},
	year = {2009},
	note = {id: 2055; PT: J; UT: WOS:000271633500006},
	pages = {544-555},
	abstract = {This study determined the natural abundance isotopic compositions (13C, 14C) of the primary carbon pools and microbial communities associated with modern freshwater microbialites located in Pavilion Lake, British Columbia, Canada. The Delta 14C of dissolved inorganic carbon (DIC) was constant throughout the water column and consistent with a primarily atmospheric source. Observed depletions in DIC 14C values compared with atmospheric CO(2) indicated effects due either to DIC residence time and/or inputs of 14C-depleted groundwater. Mass balance comparisons of local and regional groundwater indicate that groundwater DIC could contribute a maximum of 9-13\% of the DIC. 14C analysis of microbial phospholipid fatty acids from microbialite communities had Delta 14C values comparable with lake water DIC, demonstrating that lake water DIC was their primary carbon source. Microbialite carbonate was also primarily derived from DIC. However, some depletion in microbialite carbonate 14C relative to lake water DIC occurred, due either to residence time or mixing with a 14C-depleted carbon source. A detrital branch covered with microbialite growth was used to estimate a microbialite growth rate of 0.05 mm year-1 for the past 1000 years, faster than previous estimates for this system. These results demonstrate that the microbialites are actively growing and that the primary carbon source for both microbial communities and recent carbonate is DIC originating from the atmosphere. While these data cannot conclusively differentiate between abiotic and biotic formation mechanisms, the evidence for minor inputs of groundwater-derived DIC is consistent with the previously hypothesized biological origin of the Pavilion Lake microbialites.},
	issn = {1472-4677},
	doi = {10.1111/j.1472-4669.2009.00215.x},
	author = {Brady, A. L. and Slater, G. and Laval, B. and Lim, D. S.}
}
