The transfer of aquatic contaminants, including mercury (Hg), to terrestrial food webs is an often-overlooked exposure pathway to terrestrial animals. While research has implemented the use of shoreline spiders to assess aquatic to terrestrial Hg transfer, it is unclear whether Hg sources, estimated from isotope ratios, can be successfully resolved to inform site assessments and remedy effectiveness. To examine aquatic to terrestrial Hg transfer, we collected shoreline spiders (Tetragnatha spp.) and aquatic insect larvae (suborder Anisoptera) across a mosaic of aquatic and shoreline habitats in the St. Louis River and Bad River, tributaries to Lake Superior. The fraction of industrial Hg in sediments was reflected in the δ202Hg values of aquatic dragonfly larvae and predatory fish, connecting benthic Hg sources to the aquatic food web. Shoreline spiders mirrored these aquatic Hg source signatures with highly positive correlations in δ202Hg between tetragnathids and dragonfly larvae (r2 = 0.90). Further assessment of different spider taxa (i.e., araneids and pisaurids) revealed that differences in prey consumption and foraging strategies resulted in isotope differences, highlighting the importance of spider taxa selection for Hg monitoring efforts.
|Title||Mercury isotope values in shoreline spiders reveal transfer of aquatic mercury sources to terrestrial food webs|
|Authors||Sarah E. Janssen, Christopher James Kotalik, Collin Eagles-Smith, Gale B. Beaubien, Joel C. Hoffman, Greg Peterson, Marc A. Mills, David Walters|
|Publication Subtype||Journal Article|
|Series Title||Environmental Science and Technology Letters|
|Record Source||USGS Publications Warehouse|
|USGS Organization||Columbia Environmental Research Center; Forest and Rangeland Ecosys Science Center; Upper Midwest Water Science Center|