Meta-analysis of environmental factors that influence the relative decay rate between Enterococcus and Escherichia coli in aquatic environments

Abstract

For many decades, Escherichia coli and Enterococcus have been used as fecal indicator bacteria (FIB) to evaluate water quality. The decay rates of these two FIBs, and hence their persistence in the environment, vary significantly across space and time. Ongoing debates persist regarding whether the use of dual FIBs provides a more accurate assessment of health risks compared to a single FIB, and whether one FIB is more advantageous than the other in specific water bodies (e.g., freshwater vs. marine). However, many national and international regulatory bodies apply a single set of reference standards—based on concentrations of either one or both FIBs—across a wide range of geographical regions.

In this study, we conducted meta-regression and meta-analysis of data from published studies across diverse geographical regions and experimental settings to assess how abiotic factors in aquatic environments influence the relative decay rates of E. coli and Enterococcus. Our results indicate that sunlight intensity and temperature are the most significant abiotic factors affecting the relative decay rates between E. coli and Enterococcus. Contrary to the common assumption that E. coli persists longer than Enterococcus in seawater, we found that salinity has no observable effect on their relative decay rates. These findings suggest that using a single FIB may be inappropriate year-round, even at a fixed location, due to seasonal variations in sunlight intensity and duration.