Duvall, Melvin R.
Ph.D. (Doctor of Philosophy)
Department of Biological Sciences
Groundwater--Mexico--Yucatán (State); Groundwater ecology; Microbiology; Geobiology; Latin American studies
The karst aquifer in Yucatan Peninsula, Mexico, serves the population as their only drinking water source, and is extremely vulnerable to pollution from sewage and agricultural practices. Because the native microbes are expected to handle this organic pollution load, this study was conducted in order to characterize the phylogenetic and metagenomic composition of these communities as well as microbe-mineral interaction in this virtually metal-free water. Three karst sinkholes and an abandoned drinking water well at a hotel territory were sampled at fresh, saline, and fresh-saline water interface during dry and rainy seasons. The phylogenetic analysis showed an overall high microbial diversity, which was highest at the sites with anthropogenic influence and lowest in sites with high amount of sunlight. Fecal bacteria were not prevalent outside the hotel well. The metagenomic analysis revealed relatively high levels of heavy metal and antibiotic resistance, as well as numerous aromatic hydrocarbon degradation pathways. Rich sulfur and nitrogen cycling is evident on both organismal and genomic level, although there is a small discrepancy between the organisms detected in the water and the lack of nitrogen metabolism genes. Addition of minerals showed that the microbial diversity was increased most by iron-containing minerals. At the interface and saline layer, the microbes enhanced the precipitation of sulfur and framboidal pyrite. Overall, a highly diverse microbial communities are present in the Yucatan groundwater, sustained by permanently warm temperatures and high nutrient input from human activity. While this diverse microbiome may contribute greatly to mineralizing the organic pollution load, the high amount of fecal bacteria in the hotel groundwater suggests that more stringent groundwater protection measures are needed in order to preserve the only freshwater source of the peninsula.
Moore, Anni, "Characterization of the native microbial communities in the karst aquifer of Yucatan Peninsula, Mexico" (2014). Graduate Research Theses & Dissertations. 1753.
Northern Illinois University
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