Context Behind Memphis Aquifer
The Memphis Aquifer is only one part of a complex system, comprised of three different aquifers and layers of silt, rock, and sand.
There are two other aquifers below the Memphis Aquifer: the Fort Pillow and McNairy Aquifer. The system holds 100 trillion gallons of water, is 3,500 feet deep, and spans over 7,500 square miles. The stored water is naturally filtered by the different layers, and the majority of the water that is pumped out of the Aquifer is over 2,000 years old with very few contaminants. One essential part of the aquifer system is the protective confining layer of clay directly above the Memphis Aquifer, but over the years, it has been harmed by local Shelby County human activity, like coal ash storage ponds near the Mississippi river. ​
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Because of the decades of human activity, portions of the protective upper layer of clay are deteriorating, so parts of the clay layer are either missing or thinning, leading to the creation of breaching sites. As a result, the Memphis Aquifer is being exposed to dangerous pollutants, and soon, those pollutants will be found in the 100 trillion gallons of stored groundwater.
CAESAR, Center for Applied Earth Science and Engineering Research at the University of Memphis, has found 6 known and 36 suspected breach sites throughout the Shelby County, TN area. However, with the threat of breach sites, there is concern in the quality of the water systems that feed into the Memphis Aquifer and are located within breach sites.​
“Streams give water to the aquifer at different rates, in different places, and at different times of the year.”
Brian Waldron, the director of CAESER
Photo of Nonconnah Creek
Impact of Water Streams and Breach Sites
At specific times of the year, the Loosahatchie and Wolf Rivers and Nonconnah Creek feed into the Memphis Aquifer, but Shelby County facilities have reported discarding approximately 460,000 pounds of toxic pollution via water, polluting local waterways. Therefore, with the presence of breach sites, they make the Memphis Aquifer vulnerable to contaminated surface water and groundwater. Also, the Loosahatchie River, Wolf River, and Nonconnah Creek are susceptible to pollution, further threatening the Memphis Aquifer.
Why Microbes Matter
Not only can microbes play a role in facilitating bioremediation and breaking down pollutants, but they can also be used to indicate the quality of their enviornment, such as a river or creek.
The Specific Microbes
These two specific microbes can indicate the soil quality, so they can be used to make inferences about the state of certain rivers and creeks, allowing us to assess how pulluted they are and gauge how much of a threat these waterways are to the quality of the Memphis Aquifer and stored groundwater.
Pseudomonas fluorescens
The Pseudomonas species plays a crucial role in bioremediation, plant growth encouragement, and suppression of plant diseases. The Pseudomonas fluorescens bacteria assists with decomposing organic matter, facilitating self-purification processes, and circulating elements. They exist in a wide range of temperatures, specifically from 4 to 42 degrees Celsius, and if present in soil samples, they can indicate good soil fitness, or health, and reduce the amount of nitrates and nitrites, common groundwater pollutants.
Cryptosporidium parvum
This is a waterborne parasite, and it causes diarrheal disease in cattle and humans. Transmission occurs by those organisms coming in contact with contaminated water sources, such as lakes, rivers, and municipal drinking water. Additionally, it can be spread through contact with contaminated soil or infected hosts, so the presence of this bacteria in soil samples can suggest poor water quality and contamination.