Assessment of faecal pollution and relative algal abundances in Lakes Oconee and Sinclair, Georgia, USA

Abstract

Water quality was assessed for five subregions of Lake Oconee and Lake Sinclair in Georgia, USA. The areas were chosen for their levels of human impact, including: (i) suburban development >30 years old; (ii) modern suburban development; (iii) industry; (iv) agriculture; and (v) an area of low human activity. The measured temperature, pH, dissolved oxygen concentration and turbidity values were normal for oligotrophic lakes. Faecal pollution in the lakes was determined using the membrane filtration method (Method 1600) on mEI plates for enterococci. There was a positive correlation between turbidity and the number of faecal enterococci in the lakes. The faecal pollution level was higher for the old suburban and agricultural areas. Faecal pollution in the agricultural region of Lake Oconee exceeded EPA regulatory standards. The faecal pollution source was identified using polymerase chain reaction detection, with Bifidobacterium adolescentis being a marker of human faecal pollution, and bovine-associated Bacteroides (BoBac) as a marker of cattle faecal pollution. Human faecal pollution was detected in the agricultural, old suburban and industrial areas of the lakes. In contrast, bovine faecal pollution was detected only in the agricultural area of Lake Oconee. Measurements of chlorophyll-a and relative algal community abundance indicated the least-impacted and modern suburban areas had significantly lower numbers of primary producers, being dominated by diatoms.

Detection of <i>Stx</i>2 Gene of <i>Escherichia coli</i> and Elevated Levels of Fecal Bacteria in the Cattle Farming Regions of Lake Oconee

“…At the beef cattle site BC1, cattle have direct access to surface water which subsequently led to the highest geometric means of E. coli and enterococci ( Table 5). This agrees with previous research that demonstrated that high level of fecal bacteria were present in the cattle this farming region of the Oconee Watershed [8,19]. Most of the areas where cattle were present, except for the cattle farming site BC3, exceeded the state regulatory standard for E. coli levels of 126 CFU/100mL in recreational waters [22].…”

“…The physiochemical parameters DO, pH and temperature were similar at all the study sites, and turbidity was higher at the cattle farming sites (~55 NTU) compared to the cattle free regions (~36 NTU) of the watershed (Table 2). These parameters are typical for surface waters in the Lake Oconee region [8,19]. Surface water from dairy and beef cattle farming areas exhibited similar physical parameters throughout the course of the study.…”

“…Research on the sources of fecal pollution in the Oconee River Basin is very limited, but poultry and cattle opera- tions along with urban development have been suggested as major sources of fecal bacteria in the Oconee Watershed [8,19,21]. Whenever there is a high incident of cattle fecal contamination in an environment there will be an increase in the likelihood of detecting STEC including E. coli O157:H7 in that area because cattle are a natural reservoir of these pathogenic bacteria [6,22].…”

“…In contrast, relatively low levels of fecal bacteria including E. coli were detected in the forested and urban areas of the watershed ( Table 3). Low levels of fecal pollution are typical for forested and modern suburban regions of the Oconee Watershed [8,19].…”

“…Recent studies have demonstrated that the Lake Oconee Watershed is impacted by fecal pollution from urban development and cattle farming operations [8]. Burt et al 2011 used Microbial Source Tracking (MST) markers to trace the source of E. coli in the Lake Oconee Watershed to bovine and human sources, and determined that the highest concentrations of E. coli in surface water were found in the cattle farming regions of the lake.…”