The geographic variation and potential risk of DDT in the blood of Pied Kingfishers from northern KwaZulu-Natal, South Africa

Abstract

Evans, S.W. & Bouwman, H. 2000. The geographic variation and potential risk of DDT in the blood of Pied Kingfishers from northern KwaZulu-Natal, South Africa. Ostrich 71 (1 & 2): 351–354.

DDT has, since 1946 been used in the intradomicilliary control of malaria in northern KwaZulu-Natal. The Pied Kingfisher was selected as representative for organisms in relatively high trophic levels. Blood was obtained from Pied Kingfishers at Kosi Bay (n = 5), Pongolo Floodplain (n = 13), Mkuzi Nature Reserve (n = 4), Ndumu Nature Reserve (n = 4) and St Lucia (n = 3), extracted and analysed [SWEl] via gas chromatography. The highest blood DDE and σDDT concentrations were obtained for the birds from the Pongolo Floodplain (means of 95.92 μg 1⁻¹/107.01 μg μg 1⁻¹) and Kosi Bay Nature Reserve (means of 189.09 μg 1^−l/241.8 μg 1⁻¹). DDT was detected in the blood of Pied Kingfishers from Kosi Bay (mean 47.14 μg 1⁻¹) and Pongolo Floodplain (mean 44.34 pg 1⁻¹) only. This indicated their proximity to DDT application and the greater influx of DDT and its metabolites into the water component of these systems. The EDDT plasma concentrations in the Pied Kingfisher blood were calculated by multiplying the blood values of σDDT by 1.8. Using the regression, log₁₀Y = 0.7785 + 0.8593 (log₁₀X), relating the σDDT in eggs to σDDT in plasma of American Kestrel Falco sparverius it was possible to calculate the mean Pied Kingfisher egg σDDT concentration. The approximate mean Pied Kingfisher egg concentration of σDDT was calculated at 2.26 mg kg⁻¹ for Kosi Bay and 1.24 mg kg⁻¹ for the Pongolo Floodplain. Using the highest calculated plasma value of σDDT for Kosi Bay and the Pongolo Floodplain indicated that egg σDDT concentrations could be as high as 4.01 mg kg⁻¹ and 4.17 mg kg⁻¹ respectively. These calculated levels may be significant when compared to levels of DDE, known to have a detrimental effect, in the eggs of the Brown Pelican Pelecanus occidentalis, where a concentration of 2.5 to 3 mg kg⁻¹ was associated with substantially impaired reproductive success. The highest calculated egg concentration was nearing this level and it is therefore possible that the Pied Kingfisher population may be at risk.