Changes in Microbial Water Quality Associated with an Extreme Recreational Water Event in Ohio, United States

Abstract

Extreme bather densities can have significant impacts on water quality in treated and untreated waters. In this case study, water quality was monitored throughout an annual event known as the “Mirror Lake Jump,” in which thousands of ‘jumpers’ briefly entered a small lake fed by a municipal water supply, which provided an exceptional opportunity to track the water quality change due to extreme bather levels in a short period of time. Microbial water quality was monitored in conjunction with enumerating bathers, mostly collegians, fully exposing their body to the water, which occurred in an urban pond (2600 m3) on a university campus in Ohio, U.S.A. Microbial densities were determined from water samples collected before, during, and after the event. Quantification of fecal indicator bacteria (Escherichia coli, enterococci) and genetic markers reflecting fecal contamination (gyrB, HuBac, tetQ, ent23) was performed using culture-based methods and quantitative polymerase chain reaction (qPCR), respectively. Significant correlations (p < 0.05) were observed between the total number of jumpers and levels of turbidity, enterococci, E. coli, a human-associated marker (HuBac), and an antibiotic resistance marker (tetQ). Among bacteriological parameters, the tetQ marker presented the most significant time-associated trend (p = 0.01). Overall, the fecal indicator bacteria (FIB) densities observed during this extreme event ultimately exceeded water quality action values by an order of magnitude. Bather fecal shedding and resuspension of FIB and antibiotic-resistant bacteria likely occurred during the Mirror Lake Jump and future studies related to bather density impacts on microbial water quality are recommended for improving understanding related to potential public health impacts.