Chlorinated, brominated, and fluorinated organic pollutants in Nile crocodile eggs from the Kruger National Park, South Africa

Repeated annual episodes of Nile crocodile deaths in two isolated areas of the Kruger National Park prompted the investigation of possible organohalogen pollutant involvement. Crocodile eggs were collected close to one of the mortality sites (Gorge) as well as from a crocodile farm (CF) as reference. Sigma DDT as significantly higher in Gorge (450 ng/g wm) than in CF eggs (85 ng/g wet mass). Percentage DDT of Sigma DDT was significantly higher in CF (14 per cent) than in Gorge eggs (5 per cent). Mean Sigma DDT was almost 70 times higher than mean Sigma PCB in Gorge eggs. HCB, beta-HCH, mirex, brominated flame retardants (BFRs), and perfluorinated compounds (PFCs) occurred at lower concentrations. We believe that the BFR and PFCs data represent the first published results for any crocodile egg. Thickening of the outer eggshell layer of Gorge eggs was significantly associated with higher concentrations of Sigma DDT. Concentrations of Sigma DDT and other pollutants were in the same range as eggs from elsewhere, where there were no mortalities. Concentrations of Sigma DDT in eggs from healthy Australian crocodiles were of the same orders of magnitude as the current study, making it highly unlikely that the concentrations of pollutants measured in the present study would have caused or substantially contributed towards the mortalities observed. Concerns about reproduction and behaviour remain. As large predators, crocodilians are at the apex of the freshwater aquatic food web. More research is needed to guide measures to manage African freshwater systems so that it will also sustainably accommodate these large, long-lived animals. (C) 2013 Elsevier Inc. All rights reserved.