Original Articles

Organochlorines in bottlenose dolphins Tursiops truncatus from the east coast of South Africa


Concentrations of polychlorinated biphenyls (PCBs), t-DDT (DDT + DDE + DDD) and dieldrin were determined in blubber samples of 105 bottlenose dolphins inhabiting the coastal waters of the east coast of South Africa. Residue concentrations increased with age and, in males, reached levels that may impair testosterone production. In females, however, there was a decline in concentrations of all three residues in animals with between 8 and 10 dentinal growth layer groups. A significant difference was found between residue levels in females before and subsequent to their first or second ovulation, suggesting that first-born calves receive the majority of the mother's load through lactation. Evidence is presented to indicate that primiparous females impart the majority of their load within seven weeks post-partum. Levels of PCBs, t-DDT and dieldrin differed significantly in different geographical areas, suggesting a degree of isolation of sections of the population.

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