Abstract. This article discusses the features of mercury distribution in the water of the Baikal ecosystem. We present an analysis of Hg concentrations in the surface and deep water of Lake Baikal, its outflow, the Angara River, and the largest tributaries of Lake Baikal. The study revealed that all significantly elevated mercury concentrations in Baikal water were preceded by earthquakes or geodynamic impacts. We propose a death of Baikal endemic species, Baikal seal, due to mercury intoxication.