Viable bacterial biomass and functional diversity in fresh and marine waters in the Canadian Arctic

Bacterial biomass and functional diversity in four marine and four freshwater samples, collected from Resolute Bay, Nunavut, Canada, were studied using fluorescent nucleic-acid staining and sole-carbon-source utilization. Viable microbial counts using the LIVE/DEAD BacLight Viability Kit estimated viable marine bacterial numbers from 0.7 to 1.8×106 cells/l, which were lower than viable bacterial numbers in freshwater samples (2.1–9.9×106 cells/l) (RCBD-ANOVA). Calculations of the Shannon-Wiener diversity index and average well colour development were based on substrate utilization in ECO-Biolog plates incubated at 4°C and 20°C for 38 and 24 days, respectively. The Shannon-Wiener diversity of the marine water samples was significantly greater ( x H'=2.40±0.08, P <0.005; RCBD-ANOVA) than that of freshwater samples ( x H'=1.20±0.00, P <0.005; RCBD-ANOVA). Differences in microbial diversity between fresh and marine water samples at 4°C ( x 4°C =2.01) and 20°C (x20°C =2.31) were also detected by RCBD-ANOVA analysis. Interactions between water type and incubation temperature were not significant ( F =1.926, F c=5.12). Principal component analysis revealed differences in metabolic substrate utilization patterns and, consequently, the microbial diversity between water types and samples.