Microbiological water quality of a temperate third-order stream

Livestock is an activity of the primary sector that mostly affects the microbiological quality compromising the potential uses of water. Due to the current and future demand, it is essential to generate baselines of water resources, evaluate risks, and design conservation strategies. The aim of the work was to study the microbiological water quality through indicator microorganisms such as coliform group, Escherichia coli, and aerobic sulfite reducers (ASR) in a temperate stream from Pampas ecoregion affected mainly by extensive livestock activities. A third-order stream, namely Santa Bárbara (Entre Ríos, Argentina) was studied during an annual period (2013). The highest coliform counts occurred during the sampling with higher temperatures, organic matter, and total phosphorus. The frequency of the presence of E. coli and ASR bacteria was high during winter and correlated negatively with the hydrometric level of the Gualeguaychú river and the rains. It was observed that the total and thermotolerant coliform values were very similar, which indicates that most of the coliforms were associated with a fecal origin of the livestock activities that develop in the sub-basin. Moreover, the results indicated a high risk to health due to microbiological contamination. We conclude that it is necessary to implement sustainable management techniques to reduce the impact of the livestock on the aquatic ecosystem.