Bird’s blood and feathers as bioindicators for the oxidative stress induced by metal(loid)s in polymetallic contaminated areas

Toxic metal(loid)s in polymetallic mining areas are very prominent environmental stressors and may lead to undesirable oxidative stress responses in wild birds. Finding an effective nondestructive bioindicator to monitor the toxic effects of oxidative stress induced by metal(loid)s exposure is vital for bird conservation in these areas. In this study, the contents of six metal(loid)s (Cu, Zn, Pb, Cd, Cr and As) in feathers and plasma and the levels of seven oxidative stress biomarkers (MDA, SOD, GST, GPX, CAT, GSH and GSSG) in plasma were measured and their correlations were investigated for three resident bird species (turtledove Streptopelia chinensis, sparrow Passer montanus and blackbird Turdus merula) in Tongling, a polymetallic contaminated mining area in eastern China. The contents of most metal(loid)s were high in our samples and they were positively correlated with each other in both feathers and plasma, except that the Cd content was negatively correlated with Zn in plasma. Also, the activity levels of oxidative stress biomarkers (MDA, SOD, GST, GPX and CAT) in plasma were positively correlated with each other. The Pearson correlation analysis showed that the first principal component of metal(loid)s in feathers was positively correlated with that in plasma. The canonical correlation analysis (CCA) indicated that the levels of oxidative stress biomarkers had positive correlations with the contents of As, Cr and Cd in feathers, and with the contents of As, Cr, Pb, and Zn in plasma. Compared with those in feathers, the metal(loid)s in plasma explained more of the total variance of the levels of oxidative stress and should be a good bioindicator. Due to the sampling convenience and no damages, we suggest that feathers may possibly be used as an auxiliary bioindicator for monitoring oxidative stress induced by metal(loid)s. This study supplements the information about selecting the bird-related nondestructive bioindicators as environment monitoring tool in polymetallic mining areas and provides a reference for bird conservation in similar areas