Figure 6.

Results of SSOM analysis using As as an ordering external factor: (a) sites mapped in 5 clusters, with different colors: <8 mg kg⁻¹ d.w. (blue cells), 8–10 mg kg⁻¹ d.w. (green cells), 10–16 mg kg⁻¹ d.w. (yellow cells), 16–25 mg kg⁻¹ d.w. (orange cells), >25 mg kg⁻¹ d.w. (red cells); (b) distances between clusters: high distances in yellow, low distances in red; (c) species graphs representing the different abundances of a species in the cells (values on y axis represent log₁₀-tranformed abundance): very abundant (purple cells), abundant (cyan cells), present (green cells), absent (red cells). Abbreviations of species names are reported in Table 3.