Rough-toothed
dolphins, Steno bredanensis, are
closely associated with coastal waters in the Southwestern Atlantic
Ocean, increasing the exposure to multiple stressors, such as chemical
pollution. Persistent organic pollutants (POPs) are known to affect
the health of cetacean species. To comprehend the potential impacts
of POPs on populations’ viability, it is necessary to distinguish
populations and predict their risk of long-term exposure. Blubbers
of rough-toothed dolphins (n = 28) collected along
the southeastern (SE) and southern (S) Brazilian coast were screened
for polychlorinated biphenyls (PCBs) and pesticides in a gas chromatograph
coupled to a mass spectrometer. Based on the contamination profile,
a discriminant function analysis separated the rough-toothed dolphins
into three ecological populations: two coastal and one offshore. POP
concentrations were the highest reported for the species worldwide
and highest among the delphinids in Brazilian waters, reaching 647.9 μg
g–1 lw for PCBs. The SE population presented 212.9
± 163.0, S population presented 101.0 ± 96.7, and OCS/S
population presented 183.3 ± 85.3 μg g–1 lw (mean ± SD) of PCBs. The potential risk of effects triggered
by elevated PCB concentrations was assessed in an individual-based
model. A risk of severe decline in population size is projected for
the three populations in the next 100 years, especially in SE Brazil,
varying between 67 and 99%.
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