Fig. 7.

Short chain fatty acid concentrations before and after the addition of nitrate to the microcosms. The boxplots represent the concentration of all short chain fatty acids combined (a, b) (including lactate, succinate, formate, and propionate), butyrate (c, d), and acetate (e, f) before (t = 0 min) and after (t = 6 min and t = 60 min) the addition of nitrate. The significance (p < 0.05) of the difference in acid concentration between the time points of the same treatment was tested using the Wilcoxon signed ranks test. The significance (p < 0.05) of the difference in acid concentration between the treatments at a single time point was tested using the Mann-Whitney test. The boxes represent the median and interquartile range (IQR), and outliers more than 1.5× IQR are depicted by circles and more than 3× IQR by stars