Fig. 1: Sinusoidal and long-term variability in groundwater microbiomes.

a Temporal patterns in microbial community similarity across all groundwater samples per well. Blue points represent raw Bray-Curtis similarity values plotted against pairwise sampling time intervals. Regression lines (black dashed lines) and smoothing curves (red solid lines) are added to visualize both linear turnover and potential sinusoidal trends. Turnover rates (% year⁻¹) are derived from regression slopes. Please note that y-axis is different across wells. b Temporal changes in groundwater microbial community diversity across individual wells. Each panel shows one well, with colors indicating bacterial classes whose relative abundances exceed 2%. The colors in the legend are arranged left to right, corresponding to the top-to-bottom order of taxa present in each stacked plot; however, not all taxa (and their associated colors) appear in every panel due to differences in community composition. The first six years of microbiome data at wells of H41, H43, and H52 were published in Yan et al.¹³ Sample size per well are as follows: H14, n = 89; H32, n = 125; H41, n = 117; H43, n = 118; H51, n = 119; H52, n = 124; H53, n = 123.