Total- and methyl-mercury response in brine and biota to destratification of the great salt lake, utah, usa

Measurements of the aquatic chemistry of the South Arm of Great Salt Lake were made prior to and after elimination of flow between its North and South Arms to demonstrate dramatic alteration of the system in response to sealing of the railway causeway separating the arms. Perennial stratification of oxic shallow and anoxic deep brine layers characteristic of the South Arm prior to sealing of the causeway has been replaced by a vertically homogenous oxic brine following elimination of flow between the arms. Total mercury concentration in the water column and underlying sediment decreased to approximately 20% of their pre-causeway sealing values, and methyl mercury concentrations became insignificant relative to pre-sealing values. These measurements provide new understanding of the role of the deep brine layer in promoting the highly elevated methyl mercury concentrations observed before causeway sealing. Additional mercury measurements in biota provide further information regarding the implied connection between elevated methyl mercury concentrations in the deep brine layer and elevated mercury in avian species reported prior to causeway sealing.