Fig. 1. MeHg net formation in sediment from three different Hg^II tracers in response to experimental treatments.

The graphs display average MeHg/Hg^II molar ratios ± SE (n = 3 to 9) determined in mesocosm sediments at different times in response to each of the three experimental treatments: low nutrient input (NP_low, blue triangles), high nutrient input (NP_high, green diamonds), and terrestrial NOM input (TM, red squares). Each panel displays the net methylation for the specific Hg^II isotope tracers added to the mesocosms. (A) Metacinnabar added to the sediment (β-²⁰⁰HgS_sed), (B) organic matter Hg complex added to the sediment (²⁰¹Hg^II-NOM_sed), and (C) Hg^II added to the water column (²⁰⁴Hg^II_wt). The data for the NP_low treatment were reproduced with permission from Jonsson et al. (10).