The Importance of Arachnids in the Trophic Transfer and Biomagnification of Mercury in the Terrestrial Ecosystem of the Great Salt Lake

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Jim Goodman, Westminster College


Mercury is a toxic element that adversely impacts the health of wildlife and ecosystems worldwide. While all forms of mercury are toxic, methylmercury is the only form of mercury that is biomagnified, and thus organisms with the highest mercury concentrations and most at risk to mercury toxicity are typically the top predators in an ecosystem. To evaluate if arachnids, a top predator in the insect realm, are bioaccumulating mercury a spatial and temporal study of mercury bioaccumulation in arachnids and terrestrial invertebrates was conducted at the Great Salt Lake. Total mercury (HgT) and methylmercury (MMHg) concentrations were measured in arachnids collected once each month from two different sites on Antelope Island in the Great Salt Lake, and at a control site at Utah Lake, a fresh water lake to the south where mercury concentrations in the water column are substantially lower. Average concentrations of HgT and MMHg in arachnids from Antelope Island were 2600 ± 497 ppb and 1690 ± 169 ppb, respectively. These were significantly higher than the HgT and MMHg concentrations in arachnids at Utah Lake, where they are only 72 ± 54 ppb and 42 ± 30 ppb, respectively. Substantial spatial variation in HgT and MMHg concentrations in arachnids at the two sites on Antelope Island was also documented, and may be due to differences in the abundance of brine fly prey at the different locations.