## 3 Results and Discussion  
### Septic System Density  
Concentrations of FIB were greatest in watersheds that contained the highest septic system densities (Figure 2; Table 2). Differences in the median _E. coli_ concentrations between the higher septic system density watersheds (SF3 and CS3) were statistically different (_E. coli_: \(p<0.01\); enterococci: \(p\)= 0.05) from the lower density watersheds (SF1 and CS1) but not for the intermediate density watersheds (_E. coli_: \(p\) = 0.12; enterococci: \(p\) = 0.10). Watersheds served by SF systems demonstrated clear differences in FIB concentrations based on septic system density. The SF3 watershed contained median concentrations of _E. coli_ and enterococci of 1203 MPN 100 mL\({}^{-1}\) and 253 MPN 100 mL\({}^{-1}\), respectively. Median _E. coli_ and enterococci concentrations were approximately 18 and 5 times greater than the SF1 watershed. Both _E. coli_ and enterococci concentrations in the SF3 watershed were approximately 5 times greater than the SF2 watershed (Figure 2; Table 2). Furthermore, _E. coli_ and enterococci concentrations in the SF3 watershed exceeded concentrations in the SF1 91% and 100% of the time, respectively. While median differences between SF3 and SF2 were not statistically significant, concentrations of _E. coli_ and enterococci in SF3 exceeded concentrations in SF2 73% and 82% of the time, respectively. Watersheds served by conventional septic systems exhibited a similar trend for _E. coli_ but not for enterococci (Figure 2). The CS3 watershed contained the greatest median _E. coli_ concentration (526 MPN 100 mL\({}^{-1}\)) and was approximately 3 and 7 times greater than the CS1 and CS2 watersheds, respectively (Figure 2; Table 2). The CS3 and CS1 watersheds contained similar median concentrations of enterococci of 101 and 105 MPN 100 mL\({}^{-1}\), respectively, and were approximately 1.3 times greater than the CS2 watershed (Table 2). Warmer months tended to exhibit greater FIB concentrations and variability for all watersheds. When pooling data from all watersheds based on season, warm months contained median values of _E. coli_ and enterococci of 725 and 253 MPN 100 mL\({}^{-1}\), respectively; meanwhile, the median concentration of _E. coli_ and enterococci was 149 and 70 MPN 100 mL\({}^{-1}\), respectively, during cold months. These differences were statistically significant for both _E. coli_ (\(p\) = 0.03) and enterococci (\(p\) < 0.01). Differences in the FIB concentration based on septic system density were most apparent when accounting for seasonality (Figure 2). When comparing seasonal trends based on septic system density, the lower density watersheds (CS1 and SF1) exhibited statistically significant differences based on season for _E. coli_ (\(p\) = 0.04) and enterococci (\(p\) < 0.01) concentrations. Differences in median concentrations of enterococci (\(p\) = 0.03) were statistically significant for intermediate density watersheds (CS2 and SF2), but not for _E. coli_ (\(p\) = 0.23). The higher density watersheds (CS3 and SF3) did not exhibit statistical differences for either _E. coli_ (\(p\) = 0.52) or enterococci (\(p\) = 0.69). Past studies have found seasonal variability in FIB communities within surface waters due to wildlife and pet activity [7; 35], sediment agitation via recreation or storms [36], snowmelt [37], and/or rainfall [36; 38]. In the current study, elevated FIB concentrations in warmer months were likely due to increased wildlife and pet activity [7; 35]. The lack of a significant temporal trend in the higher density septic watersheds may suggest that spatial differences in septic system density exhibit a stronger influence on river FIB communities than temporal fluctuations. Past studies also found that spatial variability affected river bacterioplankton communities more than seasonal variation [39; 40; 41; 42; 43]. FIB communities may be affected by, but not limited to, changes in salinity [40], reduced river flow and sedimentation rates [42], and land use [24; 40; 41; 43].