Tissue metal concentrations and toxicity in wild turkeys following chronic exposure to mining-contaminated soils in southeast Missouri, USA
The Big River watershed in southeast Missouri (SEMO) is a Superfund site with an extensive history of lead (Pb) and zinc (Zn) mining; cadmium (Cd) and other metals also occur in the ore and waste materials. We examined whether SEMO wild turkeys ( Meleagris gallopavo ) exposed to mining-contaminated floodplain soils and food resources in the Big River watershed had elevated metal concentrations in their tissues, indicating Pb poisoning and associated toxic effects. Compared to reference birds ( n = 15) harvested in northern Missouri, SEMO turkeys ( n = 23) had significantly elevated Pb concentrations in ventricular content, liver, kidney, bone and contour feathers. Liver and kidney from SEMO turkeys also contained significantly elevated Cd concentrations compared to reference birds. Grit (2.8–5.6 mm) from turkeys ( n = 1 reference; n = 6 SEMO) was within the size range of coarse sediments reported to contain toxic metal concentrations, and 63% of turkeys harvested within 4 km of the Big River floodplain had tissue concentrations that exceeded avian thresholds for Pb poisoning. Tissue concentrations of Pb were significant predictors of keel hemorrhage as well as reductions in testis weight and bone Zn concentration. These sublethal endpoints suggest that chronic metal exposure in SEMO turkeys may be inducing toxic effects at lower tissue metal concentrations than would be estimated by current avian toxicity thresholds. These findings highlight the need for decision makers to consider how metal contamination may affect local turkey health and abundance, and the need for data-driven guidance for the safe consumption of wild foods harvested in SEMO and other mining-affected sites.