Bacterial communities of rivers with differing sources of pollutants.

Rivers contain a large array of life from bacteria to trout and are often a source of drinking water for cattle, rivers also provide food for human consumption. Contamination from agricultural run-off, waste water treatment plants and urban run-off all contribute to the degradation and pollution of water quality which in turn is a major risk to human health.

In this study the authors investigate the bacterial community composition in low flowing river water from different sources of pollutants. There were fourteen sample locations which included two different waste water treatment plants (WWTPs) along the river Santa Ana River (SAR) in Southern California, USA.

The authors used a grab method to collect water from 10 – 15 cm from the surface of the river, with collections being made in normal weather and after storms. Molecular methods Terminal Restriction Fragment Length Polymorphism (TRFLP) and Polymerase Chain Reaction (PCR) on samples collected, physical and chemical parameters were also measured. Nonmetric Multidimensional Scaling (NMDS) was used to analyse data within the parameters of Wisconsin transformation and Bray-Curtis index. An Analysis of Covariance (ANOCOVA) and Tukey HSD test were also used for testing significance.

The authors found that three phyla were dominant throughout all of the samples; Proteobacteria, Bacteroidetes and Cyanobacteria. There was no significant difference of bacterial contamination between the agricultural and urban run-off sample sites although there was a significant difference for community structure between the agricultural/urban run-off and the WWTPs sites which was confirmed by hierarchical clustering analyses. The results did show that the storms significantly affected the total bacteria counted.

The authors conclude by claiming that the use of molecular methods and recording environmental (both physical and chemical) conditions they can understand some of the relationships between microbial communities. They have shown a direct link to effects of storms on the flow of the river and how these storms have affected the bacterial communities. The authors themselves admit that their data set was not very large and a more comprehensive investigation is required, this is a good start however for varying effects of anthropogenic activities on river bacterial communities.

A review of: Ibekwe, A. M., Leddy, M. B., Bold, R. M., & Graves, A. K. (2012). Bacterial community composition in low-flowing river water with different sources of pollutants. FEMS microbiology ecology, 79(1), 155-66.