Far from the coast: organohalogen bioaccumulation in spinner dolphins from the Southwestern Atlantic

Organohalogenated compounds (OCs) are persistent, toxic, and easily transported in the environment. They bioaccumulate in biota and biomagnify along trophic webs, reaching high concentrations in top predators, such as odontocetes. Although data on OCs in South Atlantic oceanic species are limited, these compounds have been detected in dolphins far from pollution sources. This study evaluated the levels and contamination profile of organochlorine (PCBs, DDTs, HCHs, HCB, and mirex) and organobromine compounds (PBDEs, MeO-BDEs, HBB, and PBEB) in spinner dolphins (Stenella longirostris) from the outer continental shelf and slope of southeastern and southern Brazil. Remote biopsies of subcutaneous adipose tissue were collected (n = 42) and grouped by region (southeastern: n = 33; southern: n = 9). Discriminant analysis was conducted to assess differences in the contamination profile; five subgroups were found and defined by oceanographic features. PCBs were predominant in the Southeast (Sub-areas 1 and 2) while DDTs in the South (Sub-areas 3, 4 and 5). Concentrations (in ng/g lw) ranged from <11.90 to 15,344 for ΣDDT; <10.70 to 13,267 for ΣPCB; 1521.4 to 12,152 for ΣMeO-BDE; <18.30 to 3139.7 for Mirex; and <1.00 to 324.7 for ΣPBDE. HCHs, HCB, HBB, and PBEB were below the quantification limits. Mirex concentrations were among the highest reported in South Atlantic delphinids. Three assemblages (Sub-areas 1, 2 and 3 + 4 + 5) were identified, suggesting different foraging areas related to oceanographic processes. These results reveal cross-regional environmental dispersion and bioaccumulation in oceanic top predators of organohalogenated compounds, suggesting that coastal pollution can significantly impact the conservation of oceanic species.