A Biogeochemical Description of Microbial Biofilms from Fowl Cay Reef and Microbial Mats at Salt Pond, the Bahamas

Reef environments and hypersaline ponds, such as those present in The Bahamas, possess unique microbial mats and biofilm communities that play a significant role in the formation of stromatolites and reef rock. Microbial mats and biofilms have been linked to the formation of these boundstones that can be substrates for larger organisms indigenous to these diverse communities. This preliminary assessment aims to measure the spatial dynamics of the microbial communities and associated chemical microgradients to provide further understanding of these complex environments. This research describes the change in biogeochemical composition of the microbial mats and biofilms at different depths on the reef and different salinities at the pond. The presented work focuses on the microelectrode profiling of the microbial structures to determine the concentrations of O₂ and H₂S and variations in redox potential and pH, as part of the larger project goal to document the shifts in microbial community composition using carbon substrate utilization profiles, light microscope, and scanning electron microscopy (SEM). In addition the project aims to distinguish carbonate precipitates from biotic components using confocal microscopy. We hypothesize that measured microbial community, structure, and chemical microgradients significantly vary with reef depth and pond salinity, where microbial communities found within each mat/biofilm environment show distinct relationships with the carbonate precipitates present at each site. Preliminary chemical microgradient and microbial community results substantiate this hypothesis where variations with salinity and depth were found. Additionally, comparisons between the reef and hypersaline pond locations revealed distinct microbial and biogeochemical features between sites. Initial SEM analysis of the reef biofilm showed diverse micobiota including the presence of diatoms, coccoliths, bacteria, and an abundance of organic material illustrating the diversity of reef environments at the microscale. Further, microelectrode profiles and confocal lense analysis from each transect interval at the two research locations will be discussed.