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Variation in total mercury content of spiders from coal-impacted areas in Central Pennsylvania

Mercury is an important and persistent pollutant in the state of Pennsylvania but its transport between terrestrial and aquatic food chains is poorly understood. We measured mercury levels among spider taxa near various coal-impacted areas adjacent to or away from aquatic systems. These areas were compared to agricultural and headwater stream reference sites. Mine fire sites had the highest mercury levels in spiders. Riparian zones just upstream of a powerplant had significantly lower mercury levels than downstream and headwater streams had levels as high as powerplant-adjacent sites. We also found significantly higher mercury among riparian spiders near the powerplant compared to agricultural sites. Spider size was unrelated to mercury level. Ground spiders are particularly good bioindicators of mercury mobilization across aquatic and terrestrial interfaces within coal-impacted areas. Aquatic sources are important, but not necessary for significant trophic transfer among terrestrial arthropod predators.