Biogeochemical Stratification and Carbonate Dissolution-Precipitation in Hypersaline Microbial Mats (Salt Pond, San Salvador, The Bahamas)

Abstract

Microbial mat communities host complex biogeochemical processes and play a role in the formation of most carbonate rocks by influencing both carbonate precipitation and dissolution. In this study, the biogeochemistry of microbial mats from the hypersaline Salt Pond, San Salvador, Bahamas are described using scanning electron microscopy, X-ray diffraction, microelectrode profiling, fatty acid methyl esters, and carbon and nitrogen analyses. These microbial mats are distinctly layered both chemically and with regard to composition of microbial community, where significant (q \ 0.05) differences are noted between layers and cores. Furthermore, an oxic upper zone and an H 2 S-rich lower zone dominate the Salt Pond microbial mats, where H 2 S concentrations were measured approaching 8 mM. The high H 2 S concentrations along with the lacking evidence of mineral precipitation in SEM images point to the prevalence of carbonate dissolution. Moreover, the high concentrations of organics (3-9%) reveal that the mats are self-sourcing and can provide ample fuel to sustain the highly active heterotrophic (both aerobic and anaerobic) metabolism. Seasonal differences in sulfide and oxygen concentrations in Salt Pond mats indicate that the carbonate dissolution and precipitation reactions are dynamic in this hypersaline lake.

Millimeter‐scale resolution of trace metal distributions in microbial mats from a hypersaline environment in Baja California, Mexico

“…The reasons for the observed coherent trends in trace metal profiles can be ascribed to geochemical processes, bacterial population distributions, and differential mass transport within the mats. In modern marine stromatolites, biogeochemical and microbial processes (cyanobacterial photosynthesis, sulfate reduction, and anaerobic sulfide oxidation) are responsible for micrometer-scale CaCO 3 precipitation, whereas aerobic respiration and aerobic sulfide oxidation cause CaCO 3 dissolution Dupraz & Visscher, 2005;Dupraz et al, 2009;Puckett et al, 2011). First-order increase trends in sulfide concentration with depth in the mat have been reported (e.g., Jørgensen et al, 1979;Revsbech et al, 1983;Canfield & Des Marais, 1993) arising from localized bacterial sulfate reduction and/or other sulfur metabolisms (Fike et al, 2008).…”

Trends and Future Projections for Marine Biogeochemistry Research in Indonesia (Tren dan Proyeksi Penelitian Biogeokimia Laut di Indonesia)

“…2011-2013), microbial ecology research related to biogeochemistry tended not only in redox chemistry. Various topic independently provide new data and information, from carbonate dissolution (Puckett et al, 2011) to organic matter mineralization (Weston et al, 2011), from aquatic surface microlayers (Cunliffe et al, 2011) to denitrifications in aquatic sediments (Hunting and van der Geest, 2011). Organic matter and sediment are the leading topics in 2012, accounting for about 11.0% of 117 publications.…”

Non-lithifying microbial ecosystem dissolves peritidal lime sand

“…In core porewaters, sulfate depletions relative to chlorinity represent net microbial sulfate reduction in excess of the observed sulfide concentrations. In iron-poor carbonate sediments, most of the sulfide produced is reoxidized 24 , 25 . Sulfate excesses of up to 18% indicate that sulfide is not always reoxidized in situ, as tidal advection moves sulfidic water through the subsurface and imports oxic and sulfate-rich seawater into the subsurface.…”