Abstract
Microbialite-forming communities interact with the environment and influence the precipitation of calcium carbonate through their metabolic activity. The functional genes associated with these metabolic processes and their environmental interactions are therefore critical to microbialite formation. The microbiomes associated with microbialite-forming ecosystems are just now being elucidated and the extent of shared pathways and taxa across different environments is not fully known. In this study, we profiled the microbiome of microbial communities associated with lacustrine thrombolites located in Lake Clifton, Western Australia using metagenomic sequencing and compared it to the non-lithifying mats associated with surrounding sediments to determine whether differences in the mat microbiomes, particularly with respect to metabolic pathways and environmental interactions, may potentially contribute to thrombolite formation. Additionally, we used stable isotope biosignatures to delineate the dominant metabolism associated with calcium carbonate precipitation in the thrombolite build-ups. Results indicated that the microbial community associated with the Lake Clifton thrombolites was predominantly bacterial (98.4%) with Proteobacteria, Cyanobacteria, Bacteroidetes, and Actinobacteria comprising the majority of annotated reads. Thrombolite-associated mats were enriched in photoautotrophic taxa and functional genes associated with photosynthesis. Observed δ13C values of thrombolite CaCO3 were enriched by at least 3.5‰ compared to theoretical values in equilibrium with lake water DIC, which is consistent with the occurrence of photoautotrophic activity in thrombolite-associated microbial mats. In contrast, the microbiomes of microbial communities found on the sandy non-lithifying sediments of Lake Clifton represented distinct microbial communities that varied in taxa and functional capability and were enriched in heterotrophic taxa compared to the thrombolite-associated mats. This study provides new insight into the taxa and functional capabilities that differentiate potentially lithifying mats from other non-lithifying types and suggests that thrombolites are actively accreting and growing in limited areas of Lake Clifton.
Highlights
Microbialites are carbonate buildups that form through the interactions between microbial communities and their local environment (Burne and Moore, 1987)
Microbialites can be classified based on their internal microfabrics and include the well-studied laminated stromatolites (e.g., Reid et al, 2000) and less well-known thrombolites, which are composed of unlaminated calcium carbonate mesoclots and cavities filled with detrital sediments (Kennard and James, 1986)
The lake was first characterized as hyposaline, with total dissolved solids (TDSs) that typically ranged between 15–32 g/L in the 1980s but by the late 1990s increased to 25–49 g/L (Moore, 1987; Rosen et al, 1996; Knott et al, 2003; Smith et al, 2010)
Summary
Microbialites are carbonate buildups that form through the interactions between microbial communities and their local environment (Burne and Moore, 1987). The lake was first characterized as hyposaline, with total dissolved solids (TDSs) that typically ranged between 15–32 g/L in the 1980s but by the late 1990s increased to 25–49 g/L (Moore, 1987; Rosen et al, 1996; Knott et al, 2003; Smith et al, 2010) These increases in salinity, coupled with elevations in nitrogen concentrations, have potentially altered the dominant microbial communities in the system and constrained thrombolite formation (Gleeson et al, 2015; Warden, 2016)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
