Biomarkers of oxidative status associated with metal pollution in the blood of the white stork (Ciconia ciconia) in Spain

The aim of this study was to determine the impact of specific environmental contaminants on the activities of antioxidant enzymes in terrestrial, free-living birds. To investigate this, several biomarkers and the levels of lead, mercury, and arsenic were determined in blood of white stork (Ciconia ciconia) nestlings from two different colonies located in the west of Spain that were exposed to different environmental conditions and human activities. Different biomarker and contaminant patterns were observed between the two colonies, suggesting different levels of environmental contamination. In comparison to nestlings from a natural reference area, the levels of the three hazardous elements Pb, As, and Hg were significantly higher in the colony nearby a landfill. Analysis of antioxidant biomarkers revealed significantly higher levels of glutathione and glutathione S-transferase activity in birds from the colony close to the landfill site than were found in those from the “control” area. In contrast, the levels of malondialdehyde did not significantly differ between the two sampling sites. In addition, a positive correlation between glutathione and both Hg and As has been observed. Taken together, exposure to the three hazardous elements is reflected by enhanced activity of glutathione S-transferases, and elevated levels of glutathione and malondialdehyde. White storks can therefore be considered as a suitable model species for environmental monitoring programs.