Date of Award
Salt pans form in shallow depressions in the ground where salt water evaporates leaving a hypersaline environment remaining. These pans become flooded during extremely high tides and as time progresses, this additional salt water is evaporated leaving behind more salt deposits. Marine salt pans can provide habitat for halophilic microorganisms and provide an interesting environment for study as conditions can change with both sediment and water depth. Towards the surface of sediment in salt pans, oxygen is still available, however, deeper sediments have limited oxygen availability and are likely anaerobic. Deeper sediments can also have higher salt concentrations so may provide an optimal environment for anaerobic halophiles. Samples were taken in July and October 2018, when the salt pans were dry and flooded, and from the surface and 30cm deep in the sediment. DNA was extracted and the V4 region of the 16S rRNA gene sequenced to determine the bacterial microbiome. Bacterial communities were compared between the surface and deeper samples and flooded and dry samples. Samples taken from surface sediments had more bacterial sequences than those taken from deeper into the sediment, and surface samples accounted for 73% of the 105,000 sequences in the dataset. Salt pan bacterial communities were primarily composed of members of the Proteobacteria, Bacteroidetes, Cyanobacteria, and Planctomycetes, although a total of 21 distinct bacterial phyla were detected. These phyla differed in their distributions, with members of the Bacteroidetes, Cyanobacteria, Planctomycetes, and Chloroflexi being mainly associated with surface sediment, and Proteobacteria being more prevalent in deeper sediment. Proteobacteria, Bacteroidetes, Cyanobacteria, and Planctomycetes accounted for a greater proportion of the dry (July) bacterial community, whereas members of the Actinobacteria were more prevalent in the flooded (October) samples. In conclusion, salt pans along the Mississippi Gulf Coast harbor a diverse bacterial community that differs both spatially (by depth) and temporally (by season and/or flooded versus dry conditions). These environments can become hypersaline when dry, suggesting that this diverse community is adapted to both flooding and high salinity conditions.
Lawson, Lauren A., "Bacteria in Salt Pans Along the Mississippi Gulf Coast" (2019). Honors Theses. 1028.