Study lakes and ponds were sampled for water chemistry, including dissolved organic carbon (DOC), total nitrogen (TN), total phosphorus (TP), chlorophyll a (Chla), anions, cations, major metals, carbon dioxide (CO2), methane (CH4) and aqueous total Hg and MeHg concentrations. The physicochemical properties of the water column, including temperature, pH, conductivity, and dissolved oxygen, were measured at the water surface using a YSI meter. Vertical profiles were also conducted in 3 Subarctic thermokarst ponds. Water samples were collected for Hg at the surface and 30 cm above the bottom sediments, either from shore or from a raft. Samples were collected using the clean hands, dirty hands sampling protocol for trace metals. Both unfiltered and filtered water samples were taken at each site to determine the proportion of dissolved and particle-bound total mercury (THg or Hg(II) + MeHg) and methylmercury (MeHg).