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Tundra Swan Fecal Samples Tell Us: Exposure to Lead (Pb) in Sediments May Depend on The Vegetation They Eat
Citation:
Jankowski, M., J. Reichman, Kimberly Prestbo, J. Crawford, C. Eckley, T. Luxton, AND D. Leptich. Tundra Swan Fecal Samples Tell Us: Exposure to Lead (Pb) in Sediments May Depend on The Vegetation They Eat. SETAC North America 44th Annual Meeting, Louisville, KY, November 12 - 16, 2023.
Impact/Purpose:
This work supports the development of a set of biomonitoring tools that may be used at Bunker Hill Superfund Site, a lead (Pb) contaminated area in north Idaho. Tundra swans and other waterfowl are exposed to Pb at the site and experience a range of effects, including mortality, due to incidental sediment exposure while foraging for aquatic vegetation. As the site is cleaned, it is important to limit and monitor changing Pb exposures to waterfowl over time. Because exposure varies with vegetation type, we sequenced the DNA of tundra swan fecal samples to begin to determine what species of vegetation may most limit Pb exposures. Our results indicate that Pb exposure rates varied with site and vegetation type. Future work will further validate this technique and expand upon this dataset, so that the approach can be used as part of site remedy effectiveness monitoring and restoration planning by EPA and/or partners.
Description:
Spring migrating tundra swans (Cygnus columbianus) use lead (Pb)-contaminated lateral lakes and wetlands along the South Fork of the Coeur d’ Alene River as a refueling site. Although Pb exposure is known to occur via incidental sediment ingestion, differences in physiology and foraging behaviors associated with swan sex and diet may affect overall Pb exposure level. The influence of diet and sex requires examination in order to interpret Pb concentrations in swan fecal samples collected over space and time at the site and to guide remediation and restoration activities. We therefore collected and quantified Pb concentration in 34 fecal samples from wetland surfaces and six from captured swans at wetlands varying in sediment Pb concentration (<10-7000 mg/kg). Additionally, DNA was extracted from these fecal samples and sequenced to determine host species, its sex, and vegetation recently consumed via CO1, CHD, and rbcl genes, respectively. We found that 32 of 34 field collected fecal samples were tundra swan, molecular and morphological sex determination matched 5 of 6 times, and that the swan diet was highly unique to each wetland. Although sex did not significantly influence fecal Pb concentration, Cyperaceae (water sedges) were associated with lower Pb concentrations while Sagittaria (water potato) was associated with higher Pb concentrations. Furthermore, surprisingly, swans consumed a small fraction of their presumed preferred food item (water potato) and instead exhibited a large variation in plant species in their diet including Himalayan horsetail (Equisetum diffusum). These data indicate that remediation and restoration activities may be able to consider vegetation that presents a lower exposure risk to tundra swans. However, further work is needed prior to instituting these findings in such a manner.