Microbial Community Composition in Surface Water and Sediment From Different Sources Influences Surface Water Quality in the Santa Ana River Watershed.

Surface water may be contaminated by the release of contaminants from non point sources or release of contaminants from sediments after storm events. In this study, we characterized microbial community composition in a large watershed affected by contaminants from different sources using surface water and sediment sample. Total bacterial DNA was extracted from water and sediment samples and PCR-DGGE was performed to determine major bacterial composition. We also used sequences analysis to show phylogenetic relationships among different zones of the watershed and between sediment and water samples. The analytical scheme was divided into four zones: control and waste water treatment plant (WWTP), urban runoff, agricultural runoff, and mixed samples from the above sources. Differences in bacterial population was greatest between water (four phyla) compared to sediment (10 phyla) samples from channels dominated by agricultural runoff. Water samples were dominated from taxonomic groups within the phyla Cyanobacteria (15%), Proteobacteria (25%), Bacteroides (22%),Verrumicrobia (4%), and the rest were uncultured microorganisms. In the sediment, additional six phyla such as Spirochaetes, Gemmatimonadetes, Actinobacteria, Firmicutes, Acidobacteria, and Planctomycetes were found at different percentages.   Samples from the control and WWTP, urban runoff and the mixed samples did not show this level of differences. Therefore, microbial community composition in the sediment from agricultural runoff might be from resident bacterial population originating from livestock fecal material transported and deposited along the channel.