The microbial mats of Pavilion Lake microbialites: examining the relationship between photosynthesis and carbonate precipitation

Tuesday, 16 December 2014
Darlene Sze Shien Lim1, Ian Hawes2, Tyler J Mackey3, Allyson L Brady4, Jennifer Biddle5, Dale T Andersen6, Mark Belan4, Greg Franklin Slater4, Andrew Abercromby7, Steven W Squyres8, Mike Delaney9, Christopher William Haberle10 and Zena Cardman11,12, (1)NASA Ames Research Center, Moffett Field, CA, United States, (2)Aquatic Research Solutions, Christchurch, New Zealand, (3)University of California Davis, Davis, CA, United States, (4)McMaster University, Hamilton, ON, Canada, (5)University of Delaware, Newark, DE, United States, (6)SETI Institute Mountain View, Mountain View, CA, United States, (7)NASA Johnson Space Center, Houston, TX, United States, (8)Cornell University, Ithaca, NY, United States, (9)Marrella Underwater Services, Calgary, Canada, (10)Arizona State University, Tempe, AZ, United States, (11)Pennsylvania State University Penn State Harrisburg, Middletown, PA, United States, (12)Pennsylvania State University, University Park, State College, PA, State College, United States
Pavilion Lake in British Columbia, Canada is an ultra-oligotrophic lake that has abundant microbialite growth. Recent research has shown that photoautotrophic microbial communities are important to modern microbialite development in Pavilion Lake. However, questions remain as to the relationship between changing light levels within the lake, variation in microbialite macro-structure, microbial consortia, and the preservation of associated biosignatures within the microbialite fabrics. The 2014 Pavilion Lake Research Project (PLRP) field program was focused on data gathering to understand these complex relationships by determining if a) light is the immediate limit to photosynthetic activity and, if so, if light is distributed around microbialites in ways that are consistent with emergent microbialite structure; and b) if at more local scales, the filamentous pink and green cyanobacterial nodular colonies identified in previous PLRP studies are centers of photosynthetic activity that create pH conditions suitable for carbonate precipitation. A diver-deployed pulse-amplitude modulated (PAM) fluorometer was used to collect synoptic in situ measurements of fluorescence yield and irradiance and across microbialites, focusing on comparing flat and vertical structural elements at a range of sites and depths. As well, we collected time series measurements of photosynthetic activity and irradiance at a set depth of 18 m across three different regions in Pavilion Lake. Our initial findings suggest that all microbialite surfaces are primarily light-limited regardless of depth or location within the lake. Shore based PAM fluorometry and microelectrode profiling of diver-collected samples suggest that pink and green nodules have different photosynthetic properties and pH profiles, and that nodular growth is likely to be the primary route of calcification due to the gelatinous covering the nodule creates. On-going tests for molecular signatures and isotopic shifts will allow for further examination of surface microvariation and the associated influence on microbialite development.