45 Hydrogeology (Posters)

Added due to amount of discipline abstracts submitted.

Wednesday, 11 March 2026
9:00 AM - 12:00 PM
RCC, Lower Level Hall

Characterizing Depth Profile Patterns for Algal Toxins, Chlorophyll, and Dissolved Oxygen in J. Percy Priest Reservoir, Nashville, Tennessee

Paper number: 45-2
Program: Technical Sessions
Time: 9:00 AM – 9:00 AM

Authors

Abstract

The J. Percy Priest Reservoir in southeast Davidson County, Tennessee, is an important for drinking water, recreation, and the ecosystem for middle Tennessee.  However, there is concern that it is vulnerable to harmful algal blooms that could diminish the water quality and become hazardous.  Tennessee State University partnered with the U.S. Army Corps of Engineers, U.S. Geological Survey and Tennessee Dept of Environment and Conservation to study the occurrence and distribution of cyanotoxins and other indicators of water quality in the water column.  Understanding the distribution of cyanotoxin in waterbodies is important to risk management decisions.   The objective of this 5-month study was to characterize the vertical distribution of oxygen, chlorophyll, microcystin toxin and other parameters near the dam every two weeks from June to November, 2025. Microcystin was monitored using a series of 13 passive samplers at depths of 0, 5, 10, 15, 20, 25, 30, 40, 50, 60, 70, 80 and 90 feet swapped out every two weeks. During these sampling visits, a multiprobe sonde was used to characterize water-chemistry profile at 5-foot intervals.  Lake stratification had developed by June at 20-30 feet below the surface.  Temperatures and dissolved oxygen dropped significantly below the thermocline, specific conductance increased approximately 100 microSiemens at 20-30 feet, and chlorophyll fluorescence peaked at 15-20-feet.  Microcystin was the main cyanotoxin and the concentration peaked at a depth of 30 and 75-feet in June, 0 to 30-feet in July, 50-80 feet in August, and 70 to 80 feet in September.  These findings indicate that microcystin distribution in the water column changes during the growing season and should be monitored at multiple depths. Three-dimensional geographic information system can be used to visualize the data, increasing awareness of the water chemistry in the water column.    

Geological Society of America Abstracts with Programs. Vol. 58, No. 1

doi: 10.1130/abs/2026SE-411907

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