Investigation of contamination sources in a small urban creek using microbial source tracking and isotopic analysis

High concentrations of E. coli and nutrients have been detected in Antelope Creek, a small urban stream, in Lincoln. The objective of this study is to investigate the sources of microbes and nutrients in the watershed using microbial source tracking, nutrient isotopic analyses, and traditional water quality analyses (nutrients, E. coli quantification, etc.). Wet and dry weather water, scat, vegetation, soil, and stream-bed sediment samples were collected over a two year period (June 2013-October 2014). The scat samples were from species observed in the vicinity of the stream channel. DNA extracts from the collected samples were amplified using a PCR primer set targeting the V4 region of the 16S rRNA Gene. Sequence libraries were established using the Illumina sequencing technology. Isotopic analysis of nitrate, oxygen, and phosphate in the water, soil, and vegetation samples was also performed. Preliminary analysis using source tracking shows distinct microbial compositions among wet weather water, dry weather water, and stream-bed sediment samples. Results from nutrient and preliminary isotopic analysis suggest that atmospheric deposition may be an important contributor of inorganic nitrogen.