A 22-Site Comparison of Land-Use Practices, E-coli and Enterococci Concentrations

Land-use practices can greatly impact water quality. Escherichia (E.) coli and Enterococcus are accepted water quality indicators. However, surprisingly little research has been conducted comparing both organisms' population density relationships to land use practices and water quality. Stream water grab samples were collected monthly (n = 9 months) from 22 stream monitoring sites draining varying land use practice types in a representative mixed-land-use watershed of the northeastern United States. E. coli and enterococci colony forming units (CFU per 100 mL) were estimated (n = 396) and statistically analyzed relative to land use practices, hydroclimate, and pH, using a suite of methods, including correlation analysis, Principal Components Analysis (PCA), and Canonical Correspondence Analysis (CCA). Correlation analyses indicated significant (p < 0.05) relationships between fecal indicator bacteria concentrations, water quality metrics and land use practices but emphasized significant (p < 0.05) negative correlations between pH and instream enterococci concentrations. PCA and CCA results indicated consistent spatial differences between fecal indicator bacteria concentrations, pH, and land use/land cover characteristics. The study showed that pH could be considered an integrated proxy variable for past (legacy) and present land use practice influences. Results also bring to question the comparability of E-coli and enterococci relative to dominant land use practices and variations in pH and provide useful information that will help guide land use practice and water pollutant mitigation decision making.

Automated summary

Land-use practices have a significant impact on water quality, and the presence of Escherichia coli and Enterococcus bacteria can indicate water quality. However, there is limited research comparing the relationship between the population density of both organisms and land-use practices. This study collected stream water samples from different types of land-use practices in a mixed-land-use watershed and analyzed the bacterial colony forming units (CFU per 100 mL) using various statistical methods. The results showed significant relationships between fecal indicator bacteria concentrations, water quality metrics, and land-use practices. The study also questioned the comparability of E. coli and enterococci in relation to land-use practices and variations in pH.