ARS | Publication request: Bacterial community composition in low-flowing river water with different sources of pollutants

Submitted to: FEMS Microbiology Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 9, 2011
Publication Date: October 13, 2011
Citation: Ibekwe, A.M., Leddy, M.B., Bold, R.M., Graves, A.K. 2011. Bacterial community composition in low-flowing river water with different sources of pollutants. FEMS Microbiology Ecology. 79:155-166.

Interpretive Summary: The middle Santa Ana River (MSAR) watershed is an area that is going through many changes mainly in agriculture, open space, and rapidly growing urban areas. Therefore, the quality of the surface water varies considerably throughout the MSAR watershed. In order to address changes in water quality within the middle Santa Ana River watershed, a comparative study of bacterial population in the surface waters was performed. This is the first time that extensive studies of microbial diversity along the MSAR have been carried out. The purpose of this study was to obtain data on the microbial densities during dry-weather runoff, storm and recessional flows in the MSAR to determine seasonal and temporal variations. These communities were also examined to understand how different environmental factors (pH, salinity, turbidity, dissolved oxygen, and temperature may impact the microbial population and their densities. Salinity had a major influence on bacterial population during dry weather. During storm, there was a stong influence of temperature and dissolved oxygen and a moderate influence of turbidity on microbialpopulation. Bacterial population in wastewater treatment plants were more diverse than what was observed along channels and creeks. Changes in the bacterial population within the MSAR were caused by inputs from different sources and understanding whole microbial community structure may be a first step in identifying sources of fecal contamination to the Santa Ana River. The results of this research will be used by water quality managers from different water districts, researchers, and EPA for Total Daily Maximum Daily Load assessments for large and mixed watersheds.

Technical Abstract: Pollution of water resources is a major risk to human health and water quality throughout the world. The purpose of this study was to determine the influence of pollutant sources from agricultural activities, urban runoffs, and runoffs from wastewater treatment plants (WWTPs) on bacterial communities in a low-flowing river. Bacterial community structure was monitored using terminal restriction fragment length polymorphism (T-RFLP) and 16S rRNA gene clone library. The results were analyzed using nonmetric multidimensional scaling (NMDS) and UniFrac, coupled with principal coordinate analysis (PCoA) to compare diversity,abundance, community structure, and specific functional groups of bacteria in surface water affected by nonpoint sources. From all the sampling points, Bacteria were numerically dominated by three phyla – the Proteobacteria, Bacteroidetes, and Cyanobacteria – accounting for the majority of taxa detected. Overall results, using the b diversity measures UniFrac, coupled with PCoA, showed that bacterial contamination of the low-flowing river was not significantly different between agricultural activities and urban runoff.