Coliform bacteria in San Pedro Lake, western Mexico

Abstract

Urbanization, livestock activities, and rainfall are factors that contribute to the contamination of inland water. This study aimed to determine the spatial and temporal variability of total coliforms (TCs) and fecal coliforms (FCs) in the surface water of San Pedro Lake as well as the gills and skin of Nile tilapia (Oreochromis niloticus) cultivated in the lake. The study consisted of seasonal sampling during an annual cycle. Using the multiple‐tube fermentation technique, we quantified the microbial load of TCs in the lake and fish. The median of the TC and FC groups in surface water showed differences during the seasonal cycle, in which a significant correlation was observed between rainfall and bacterial load in the lake surface water. There was a significant seasonal difference between FCs and TCs in the gills as well as in skin FCs. Anthropogenic activities in the watershed combined with rainfall influence the bacterial load of San Pedro Lake. However, the water quality is still classified as excellent and uncontaminated according to Mexican regulations with lower FC values acceptable for higher FC values. In addition, the bacterial load in tilapia from San Pedro Lake does not pose a risk to human health. Practitioner points Watershed livestock activities combined with rainfall increase fecal matter pollution in specific areas of the lake. San Pedro Lake displays satisfactory quality for aquatic life. The median fecal coliform population in lake fish (gills and skin) differs by season.

A preliminary evaluation of microbial water quality in the irrigation pond

“…Our results suggest that surface runoff, even after light rainfall (<2.5 mm of rain) is major driver which contributing diffuse pollution both in surface and bottom waters in the pond. This result is consistent with previous studies reported positive correlation between coliform bacteria and rainfall events at lake and pond ecosystems (An et al, 2002; Jeon et al, 2019; Moshi et al, 2022; Ramos‐Ramírez et al, 2020; Staley et al, 2012; Staley et al, 2013; Stocker et al, 2019; Tryland et al, 2011; Xue et al, 2018). On the other hand, few studies reported no significant relationship between fecal indicator bacteria and rainfall (Nguyen et al, 2016; Sampson et al, 2006).…”

The water industry toolbox

“…This Issue also shows two other works related to coliform bacteria. Ramos‐Ramírez et al (2021) sample and measure the presence of coliform bacteria in a lake during an annual cycle. Total and fecal coliform have a significant seasonal evolution as a consequence of anthropogenic activities and rainfall, with higher concentrations observed during rainy seasons.…”