Interrelationships of Environmental Variables and Drivers of Ecosystem Function That Governs Fecal Bacterial Contamination in Creek Watershed.

Environmental variables are interrelated to govern ecosystem functions. Principal component analysis (PCA) were conducted to reveal the complex relationships of environmental parameters and to identify drivers in a water ecosystem.  Environmental variables included abundance, genetic diversity, and physiological characteristics of fecal indicators bacteria (Enterococci and E. coli), relevant rainfall events, as well as pH, temperature, and turbidity of water at each sampling site.  These variables in surface water and sediment of three creeks were determined at baseflow and highflow in winter and summer at eight locations for two different years.  Using targeted sampling strategy, the sampling locations represented three potential fecal matter sources, including animal production (S3), urbanization (S6) and wildlife activities (S5). Abundance (MPN 100 mL^-1) of Enterococci and E. coli were determined using IDEXX Enterolert^TM or Colilert system.  Enterococci isolates from IDEXX system were further characterized and confirmed using phenotypic and genotypic means. The percentage of IDEXX isolates confirmed as Enterococci (PPE) was obtained. Confirmed 702 Enterococci isolates were further evaluated for species diversity based on genetic variations in the intergenic spacer between the 16S and 23S rRNA genes. Of seven environmental variables evaluated, Enterococci concentration had the closest relationship with turbility, cumulative rainfall, and raifall frequency. These variables were dominant factors that contributed 55% of the detected variance.  This indicated the importance of rainfall contributing to fecal bacterial contamination in watershed. However, dominance of these variables was not as pronounce during baseflow in winter or highflow in summer, suggesting other variables were more influential to the abundance of fecal bacteria under these conditions.  Regardless of sampling time, temperature and pH were important factors loading PC2 which contributed 22% of the detected variance.  Not only had the abundance of Enterococci and E. coli but also PPE differentiated among sampling sites. The close relationships between the abundance of Enterococci and E. coli indicated that they likely share the same potential sources.  Of seven species detected, Ent. Faecalis was most dominant at all sites, composing over 50% of Enterococci detected.  However, Ent. Faecium contributed most in differentiating the sites with the exception of Site 7.  Unique Enerococci diversity was detected for site 7, which was downstream of a waste water treatment plant.