Trace elements in Pacific Dunlin (Calidris alpina pacifica): patterns of accumulation and concentrations in kidneys and feathers.

Trace element concentrations were measured in Pacific Dunlin (Calidris alpina pacifica) to identify factors that influence accumulation and to assess toxicity risks. We report concentrations of cadmium, copper, and zinc in kidneys as well as copper, lead, mercury, selenium and zinc in feathers. Relationships between element concentrations and Dunlin age, sex, bill length, habitat preference, trophic level, and sample group were investigated with regression analyses. Stable isotope ratios of carbon and nitrogen in Dunlin muscle tissue were used to determine habitat preference and trophic level, respectively. Cadmium concentrations in kidneys were significantly related to habitat preference: [Cd] in estuarine foragers >[Cd] in terrestrial foragers. Cadmium accumulation was age-dependent as concentrations increased significantly within 10 months of hatch dates but not afterward. Concentrations of cadmium and zinc in kidneys as well as lead and mercury in feathers were below those known to cause deleterious effects in birds. In contrast, selenium concentrations in feathers (range: 2.1-14.0 µg/g) were often at levels associated with toxicity risks (>5 µg/g). Toxicity thresholds are not available for copper in kidneys or copper and zinc in feathers; however, measured concentrations of these elements were within documented ranges for sandpipers. Future studies should assess potential impacts of selenium on embryonic development in Dunlin and other sandpipers. Risk assessments would yield more conclusive results for all elements if impacts under ecologically relevant stresses (e.g. development in the wild, migration, predation) were better understood.

Concentration and partitioning of metals in intertidal biofilms: implications for metal bioavailability to shorebirds.

We compared zinc, copper and cadmium concentrations and the operationally defined geochemical partitioning of the three metals in sediments enriched with biofilm versus sediments without obvious biofilm present (reference) sampled from five locations within the Fraser River Delta, British Columbia, Canada. Two-way ANOVA's with site and biofilm (enriched or reference) as the two factors were applied to determine if metal concentrations or the partitioning of the metal was dependent on the two factors. Sediment enriched in biofilm contained greater amounts of aqua regia extracted zinc and copper and tended to have greater amounts of reducible cadmium as compared to reference sediments. By contrast, reference sediments had greater concentrations of easily reducible copper suggesting differences in speciation between the two sediment types. Greater concentrations of reducible cadmium within biofilm may provide a route of contaminant exposure to shorebirds whose diet is dependent on biofilm.