Metal concentrations in selected organs and tissues of five Red-knobbed Coot (Fulica cristata) populations

The Red-knobbed Coot Fulica cristata is an abundant aquatic bird in South Africa and was anticipated to have indicator abilities for metal pollution. This hypothesis was tested on 83 coot samples collected from five selected aquatic ecosystem areas supporting substantial coot populations, of which various abiotic and biotic components are known to contain varying levels of a number of metals. The aim of this study was achieved by determining the variations in Cd, Cu, Ni and Pb concentrations in liver, kidney, bone and blood samples, with the use of standard flame atomic absorption spectrophotometry techniques. Coots from the Germiston Lake sampling site showed the highest concentrations of cadmium in liver (2.2 μg/g d.w.) and kidney (5.4 μg/g d.w.). The absence of metalprocessing industries in the catchments of the Florida Lake and the Steynsrus farm dams reflects the low liver and kidney concentrations of Cd, Ni and Cu, respectively. The blood of the Natalspruit wetland coots contained the highest dry weight concentrations of Ni (11.4 μg/g), Cd (1.8 μg/g) and Cu (14.4 μg/g). The statistical evaluation points towards small-scale geographical differences, especially in the concentrations of Cu, Ni and Pb and in the liver, kidney and blood. However, in terms of actual metal concentrations recorded, no significant differences existed between coots of the reference site (Steynsrus farm dams) and those from the other four localities. It is concluded that the impact of metal-containing diets on the tissue concentrations of these metals in birds plays a far more significant role compared to the migratory habits or short-range movements of the coots.