­­­­­­­­­­­­­­­An assessment of mercury concentrations in a terrestrial songbird at the Great Salt Lake

Background/Question/Methods

The presence of methylmercury, which biomagnifies, in a food chain can have harmful effects on organisms, including altering behavior. Mercury is typically found in aquatic ecosystems, however is also a potential problem in terrestrial ecosystems if those ecosystems are linked to food sources from the aquatic system. High levels of methylmercury have previously been found in the Great Salt Lake. We hypothesized that brine flies from the lake transfer methylmercury to the terrestrial ecosystems and to spiders, in particular. If so, then some of the highest predators included in this food chain may be songbirds that eat spiders.  We quantified mercury in the blood of the Loggerhead Shrike, Lanius ludovicianus, a species of conservation concern, on Antelope Island in the Great Salt Lake, Utah. Upon being caught, the birds were measured, color banded, and blood and feather samples collected and analyzed for mercury. In addition, brine flies, spiders, and other terrestrial arthropods were sampled for mercury.

Results/Conclusions

Preliminary bird data indicate that total mercury concentrations ranged from 0.15 to 4.00 ppm, with a mean 1.14+/- 0.31 ppm. Sub-lethal effects in other songbirds have been seen with concentrations ranging from 2.0-3.5 ppm. Thus far, 13% of shrikes tested exceeded that range. There was high variability in concentrations of mercury, which might be related to distance from shore.  Furthermore, mercury concentrations in spiders were much higher than brine flies. These preliminary data demonstrate that some mercury from the aquatic ecosystem is bioaccumulating in the terrestrial ecosystem on Antelope Island, and there may be harmful levels in the birds which could lead to change in behavior, and eventually decline in population size.