Date of Award
Master of Science
Climate change, industrial development, and thawing of permafrost all contribute to a rapidly changing Arctic, especially in terms of exposure of wildlife to contaminants. Migratory birds, the most widely distributed and abundant taxon present in the Arctic, may be ideal bioindicators to monitor contaminants and establish baselines from which future changes may be determined. I conducted two studies to determine contaminant levels and factors influencing them, measure toxicity using established thresholds and by testing blood-based biomarkers for relationships to varying trace element levels, and determine the relative sources of elements in five species of sea ducks which breed along the northern coast of Alaska: the long-tailed duck, and Steller’s, spectacled, king, and common eiders. The first study focused on levels of Se, Cd, Cu, Hg, and Pb in liver and kidneys in collected carcasses, with an emphasis on determining the patterns of variation among species, sexes (adult males versus females), and age classes (adults versus juveniles). Trace element concentrations were explained reasonably well by between-species differences in body mass, with smaller long-tailed ducks from Prudhoe Bay and Steller’s eiders from Barrow having similar concentrations of elements, and higher levels in larger species. Levels were also negatively associated with mass-specific metabolic rate and migration distance, with small long-tailed ducks and Steller’s eiders having high metabolic rates and longer migration distance. Adult male spectacled eiders had exceptionally high Se, Cd, and Cu, with Cu levels being among the highest reported for any wild bird. Pb was highest in female common eiders and juvenile long-tailed ducks, emphasizing a potential exposure risk at Prudhoe Bay, where both were sampled. Hg showed variation not explained by metabolism, migration distance, or body mass, perhaps due to local variation in exposure on breeding sites. My second study attempted to address similar questions, but with an emphasis on blood of incubating females and juveniles, and to address potential biases associated with biomonitoring in these species. The relevance of bioindicators to related taxa is assumed, but rarely tested. Common eiders are a widely-used indicator of marine environments, but few studies compare them to other species. I tested the levels of elements, their relationships to blood-based health metrics (biomarkers), and determined whether blood and feathers of the same individuals provide consistent information. Similar to my first study, levels of elements were similar in blood of long-tailed duck and Steller’s eiders, as well as between spectacled and king eiders, but common eiders had levels similar to one group or intermediate between them. Biomarker responses, however, were not consistent with element concentrations, with spectacled and common eiders having similar responses, and Steller’s and king eiders, despite differing body mass and element concentrations. Levels of Pb, and the proportion of birds sampled exceeding toxic levels, were greatest at Barrow and lower at two reference sites, emphasizing the anthropogenic source of Pb, similar to results of my first study, but in a different set of tissues. In no species were the element concentrations and biomarker responses consistent, demonstrating that use of one species to infer information on elements exposure and effects in another is not always suitable. These studies emphasized two species of particular conservation concern, the threatened Steller’s and spectacled eiders, as well as three related species. I provide baseline information on trace element concentrations in four tissue types widely used for biomonitoring of trace elements (blood, feather, liver, and kidney), and caution future biomonitoring efforts using surrogate or indicator species, as the element concentrations in sympatric species, the associations with biomarkers, and number exceeding threshold concentrations of select elements vary greatly among species. Future biomonitoring should focus on species of interest to reduce bias and better inform management decisions regarding trace elements.
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