“…In our commonly held conceptual cycle, Hg settles to the anoxic zones of lakes as less bioavailable Hg-DOM or Hg-particle complexes after deposition from the atmosphere as more bioavailable HgII (Chiasson-Gould et al, 2014). In a revised model (Figure 1), redox reactions can "reset" Hg speciation far from the air/water interface results in the incorporation of an additional source of fresh bioavailable Hg (Hg0, or its oxidation products) for methylation (Chiasson-Gould et al, 2014;Grégoire and Poulain, 2018). Under anoxic conditions, HgII reduction can occur through abiotic reactions with DOM (Gu et al, 2011) and iron-bearing minerals (Bone et al, 2014;Wiatrowski et al, 2009), but anaerobic microbes can also participate directly (Lin et al, 2014;Liu and Wiatrowski, 2018;Lu et al, 2016;Schaefer et al, 2002;Wiatrowski et al, 2006;Zhao et al, 2017).…”