The Spider Exposure Pathway and the Potential Risk to Arachnivorous Birds

There is growing concern over the health of North American birds, with evidence suggesting substantial population declines. Spiders are prominent dietary items for many bird species and mediate the transfer of contaminants to arachnivorous birds that consume them. Few studies have investigated the potential risk the spider exposure pathway poses to these birds because most studies have focused on piscivores. In the present study, we developed new chronic and acute As, Cd, Cu, Pb, Ni, Se, Zn, and MeHg spider-based avian wildlife values (SBAWVs) for multiple adult and nestling birds (primarily passerines) and then used the newly generated SBAWVs to characterize the risk to birds across 2 study areas: 1) 5 reaches in the southern Appalachian Mountains, an area with substantial mercury deposition but minimal anthropogenic impact, and 2) 4 reaches adjacent to the Emory River, an area impacted by the largest fly coal-ash spill in US history. We identified MeHg and Cu, Pb, Se, and Zn as contaminants of potential concern (COPC) at the Appalachian Mountain and Emory River study areas, respectively, based on dietary exposure of aquatic contaminants via riparian spiders. The identification of COPC at both study areas due to dietary spider exposure is notable not only because the spider exposure pathway has largely been uninvestigated at these sites but also because the aquatic systems in both areas have been studied extensively. Significant differences in MeHg concentrations were detected among spider taxa and suggest that the selection of spider taxa can impact risk characterization. These results indicate that the spider exposure pathway is important to consider when assessing potential risk, particularly for passerine birds. Environ Toxicol Chem 2020;39:2314-2324. © 2020 SETAC.