December 20, 2016
Susquehanna University biology major Hailey Shannon won Best Student Poster at the 11th annual River Symposium at Bucknell University for her research presentation on mercury levels in spiders.
Shannon, a junior from Acme, Pa., conducted the research in Centralia alongside fellow junior biology major Tara Barbarich, of Johnstown, Pa., and biology professor Matt Persons, recognized nationally for his spider research.
The 11th annual Susquehanna River Symposium was sponsored by the Watershed Sciences & Engineering Program of the Bucknell Center for Sustainability & the Environment. It connected scientists and engineers from throughout the mid-Atlantic region who study issues regarding the Susquehanna and Delaware river watersheds.
The purpose of Shannon's and Barbarich's research was to study how mercury moves through the food chain-beyond the usual mercury-containing suspects, i.e. fish. A persistent environmental pollutant, Pennsylvania has been found to be one of the leading mercury-emitting states due to the coal industry.
"Spiders have a lot of mercury and the ones that have the most tend to be ground-dwelling spiders, especially wolf spiders. So the question is, why do wolf spiders have so much mercury?" Persons said. "We most often think of mercury in fish, but we're looking at mercury that ends up in terrestrial arthropods, sometimes without significant aquatic systems, which runs counter to a lot of what we thought we knew about mercury and how it moves through food chains."
Shannon and Barbarich measured mercury levels among ground and web-building spiders at sites along the Susquehanna River near a coal-fired power plant, and compared that to spiders from uncontrolled coal fire burn sites in Centralia and Laurel Run. They also gathered samples from reference sites away from the river.
They found that spiders from mine fire sites had mercury levels 2.5 times higher than those in riparian zones adjacent to the power plant and about six times higher than those from agricultural fields or riparian zones away from power plants. Additionally, wolf spiders had mercury levels 8 to 20 times higher than insects from the adjacent water.
"Spiders are really good at concentrating mercury," Persons said, "so what we're seeing is that, as they cannibalize and prey on other spiders, mercury levels become more and more concentrated, which in turn leads to higher concentrations of mercury in the animals that feed on spiders, such as birds, frogs and reptiles."