Fig. 1. Temporal dynamics of mercury addition and recovery in the Lake 658 ecosystem.

a, Location (inset) of the Experimental Lakes Area (ELA), Canada, where Hg enriched with different isotopes was applied to the wetland, upland and lake surface of Lake 658 to simulate enhanced wet deposition of Hg (dark blue shaded area). b, Inorganic Hg added to the lake was methylated and measured as MeHg concentration in water (in ng l⁻¹; n = 516), sediments (in ng g⁻¹ dry weight; n = 1,627) and invertebrates (in ng g⁻¹ wet weight; n = 211), and as total Hg in fishes (in ng g⁻¹ wet weight; n = 1,052). Mean annual concentrations for the open-water season are shown for all lake components except for fish populations, which were collected each autumn. Concentration data for large-bodied fish are derived from body-length standardization (pike, 475 mm; whitefish, 535 mm). c, Hg loading to the lake increased MeHg concentrations (per cent increase = [lake spike MeHg]/[ambient MeHg] × 100) during the addition phase (2001–2007), then decreased during the recovery phase (2008–2015), when experimental Hg additions to the ecosystem ceased (light blue shaded area in a). Dotted lines indicate missing data.

Source data.