Boxplots represent groundwater samples from individual wells and summarize cell counts from n independent fields of view. n = 40: Samples 3–10, 12, 15–22, 24–29, 34–47, 49–51, 54, 56, 63, 67–68, 70–71. n = 39: Samples 1, 14, 33. n = 38: Sample 2. n = 20: Samples 13, 31–32, 55, 57, 61, 72. n = 12: Sample 73. For more details on individual cell counts see Supplementary Data 2 . X axis: Numbers correspond to well IDs (due to space constraints well IDs are given in Supplementary Data 1 ). Wells which were sampled at two different time points are marked with a star (*), technical replicates are marked with a plus (+). Cell abundance was determined using fluorescence microscopy and is given on a logarithmic scale. Boxplots show 1 st and 3 rd quartile, maximum and minimum values (whiskers), median (line), mean (triangle), and outlier (dots).
