Environmental dependence of metallicity gradients (∇_r[Z/H]). Left: metallicity gradients as a function of the local projected density (η_k). Right: metallicity gradients as a function of the H I deficiency (Def_HI). All galaxies are color-coded by their light-weighted stellar age (﹩\mathrm{log}{\rm{Age}}[{\rm{yr}}]﹩). In the right panel, right-pointing triangles with arrows represent galaxies with H I upper limits (lower limits for Def_HI). In each panel, the solid green line and the surrounding shaded band represent the overall trend and its uncertainty, derived from a Gaussian running median. The Spearman correlation coefficient (r) and the p-value are displayed in each panel. Gray dashed horizontal and vertical lines mark the zero-point for each parameter.