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The physicochemical properties of water samples from different outlets is shown in Table 1. The Monte Carlo test showed that RDA axes 1 and 2 were significant in elucidation of the correlations between bacterial characteristics and water physicochemical properties (F = 24.7, P = 0.008). The results revealed that water physicochemical properties had different effects on the LNA and HNA bacteria in tap water (Figure 4). It showed that the HNA bacteria (HNA%) were predominant in relative high turbidity or chrominance tap water. The reason could be that the formation of eutrophic microcosm around particulate matter would promote growth of HNA bacteria in tap water with high turbidity or chrominance (Vital et al. 2012; Liu et al. 2014). In the present study, FCM-live (LIVE) bacteria concentration showed a strongly negative correlation to cadmium (Cd) (Pearson's R = −0.964, P < 0.01), arsenic (As) (R = −0.842, P < 0.01) and conductivity (R = −0.980, P < 0.01). A negative correlation was also observed between these parameters and HNA% (Figure 4). It indicated that those heavy metals and conductivity would restrict the microbial activity and growth. In contrast, the LNA bacteria (LNA%) were positively correlated to the metal concentrations (i.e. arsenic (R = 0.889, P < 0.01) and cadmium (R = 0.977, P < 0.01)) and conductivity (R = 0.983, P < 0.01) (Figure 4). It suggested that the survival rate of LNA was higher than HNA and LNA dominated in the relative high heavy metal content or conductivity tap water. The reason could be that bacteria exhibited different susceptibility to metals (Tada et al. 2001).
Table 1

Physicochemical properties of water samples from different outlets

Physicochemical propertiesWater samples
Outlet 1Outlet 2Outlet 3Outlet 4
pH 7.62 ± 0.10 8.31 ± 0.01 8.29 ± 0.04 8.23 ± 0.05 
Turbidity (NTU) 0.195 ± 0.072 2.420 ± 0.207 2.206 ± 0.117 2.491 ± 0.097 
Water chroma (PCU) 1.585 ± 0.934 28.862 ± 0.319 21.165 ± 1.207 19.878 ± 0.051 
Nitrite (mg/L) UD 0.032 ± 0.001 0.008 ± 0.000 0.010 ± 0.001 
Phosphate (mg/L) 0.008 ± 0.001 0.169 ± 0.002 0.018 ± 0.002 0.032 ± 0.006 
Residual chlorine (mg/L) 0.055 ± 0.002 0.062 ± 0.002 0.055 ± 0.003 0.083 ± 0.001 
Ammonia nitrogen (mg/L) 1.243 ± 0.022 1.082 ± 0.022 2.346 ± 0.015 0.799 ± 0.005 
Conductivity (μS/cm2394.0 ± 1.0 365.0 ± 2.8 364.5 ± 0.7 361.0 ± 1.4 
Cd (μg/L) 0.081 ± 0.007 0.018 ± 0.005 0.023 ± 0.005 0.017 ± 0.007 
Pb (μg/L) 0.234 ± 0.011 UD UD UD 
As (μg/L) 0.492 ± 0.056 0.373 ± 0.024 0.393 ± 0.020 0.372 ± 0.021 
Cr (μg/L) 4.829 ± 0.053 5.981 ± 0.060 6.795 ± 0.102 5.418 ± 0.092 
Physicochemical propertiesWater samples
Outlet 1Outlet 2Outlet 3Outlet 4
pH 7.62 ± 0.10 8.31 ± 0.01 8.29 ± 0.04 8.23 ± 0.05 
Turbidity (NTU) 0.195 ± 0.072 2.420 ± 0.207 2.206 ± 0.117 2.491 ± 0.097 
Water chroma (PCU) 1.585 ± 0.934 28.862 ± 0.319 21.165 ± 1.207 19.878 ± 0.051 
Nitrite (mg/L) UD 0.032 ± 0.001 0.008 ± 0.000 0.010 ± 0.001 
Phosphate (mg/L) 0.008 ± 0.001 0.169 ± 0.002 0.018 ± 0.002 0.032 ± 0.006 
Residual chlorine (mg/L) 0.055 ± 0.002 0.062 ± 0.002 0.055 ± 0.003 0.083 ± 0.001 
Ammonia nitrogen (mg/L) 1.243 ± 0.022 1.082 ± 0.022 2.346 ± 0.015 0.799 ± 0.005 
Conductivity (μS/cm2394.0 ± 1.0 365.0 ± 2.8 364.5 ± 0.7 361.0 ± 1.4 
Cd (μg/L) 0.081 ± 0.007 0.018 ± 0.005 0.023 ± 0.005 0.017 ± 0.007 
Pb (μg/L) 0.234 ± 0.011 UD UD UD 
As (μg/L) 0.492 ± 0.056 0.373 ± 0.024 0.393 ± 0.020 0.372 ± 0.021 
Cr (μg/L) 4.829 ± 0.053 5.981 ± 0.060 6.795 ± 0.102 5.418 ± 0.092 

UD = undetectable.

Figure 4

Redundancy analysis plot of LNA and HNA bacterial characteristics with water physicochemical properties. Red and blue arrows represent variables of water physicochemical properties and bacterial characteristics, respectively (NH3, ammonia nitrogen; NO2, nitrite; PO4, phosphate; RCl, residual chlorine; μLNA and μHNA, the specific growth rate of LNA and HNA, respectively; LIVE and DEAD, live and dead bacterial concentration; HPC, heterotrophic plate counts; LNA% and HNA%, the contribution of LNA and HNA in total FCM-bacteria, respectively). Please refer to the online version of this paper to see this figure in colour: http://dx.doi:10.2166/aqua.2017.108.

Figure 4

Redundancy analysis plot of LNA and HNA bacterial characteristics with water physicochemical properties. Red and blue arrows represent variables of water physicochemical properties and bacterial characteristics, respectively (NH3, ammonia nitrogen; NO2, nitrite; PO4, phosphate; RCl, residual chlorine; μLNA and μHNA, the specific growth rate of LNA and HNA, respectively; LIVE and DEAD, live and dead bacterial concentration; HPC, heterotrophic plate counts; LNA% and HNA%, the contribution of LNA and HNA in total FCM-bacteria, respectively). Please refer to the online version of this paper to see this figure in colour: http://dx.doi:10.2166/aqua.2017.108.

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