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On November 5th, 2015, the Fundão dam collapsed in Minas Gerais, southeastern Brazil, releasing millions of cubic meters of mud containing mining residue into the Doce River. Two weeks later, the mud arrived to the marine environment, triggering changes in franciscana dolphin habitat, Pontoporia blainvillei , from Franciscana Management Area Ia. This is an isolated population of the most endangered cetacean species in the South Atlantic Ocean. Organohalogen compounds (OHCs) may pose a threat to this endangered population because of their endocrine disrupting properties. Hence, this study sought to determine if there were differences in the bioaccumulation profile of OHC (PCBs, DDTs, Mirex, HCB, HCHs, PBDEs, PBEB, HBBZ and MeO-BDEs) in franciscana dolphins before and after dam collapse and to build a temporal trend. Blubber of 33 stranded individuals was collected in Espírito Santo state for organohalogen assessment between 2003 and 2019. Differences were found between franciscana dolphins collected prior to and after the disaster. Additionally, significant temporal trends for organochlorine pesticides and natural and anthropogenic organobromine were detected. The increase in pesticide concentrations after 2015 is suggestive of their reavailability in the environment. The decline in organobromine over time could be due to their debromination in the marine environment and alterations in the composition of their natural producers. PCBs remained stable during the period of the study. Our findings show an increase in endocrine disruptor concentrations, which is of great concern for this endangered population. [Display omitted] • Fundão dam collapse triggered environmental shifts in franciscana dolphins' habitat. • Comparison in contaminants concentrations were done pre and post dam collapse. • Pesticides increased after the dam collapse and could affect population viability. • Naturally-produced organobromine decreased in franciscana dolphins between 2003 and 2009. • PCB levels were stable over time in franciscana dolphins between 2003 and 2009. [ABSTRACT FROM AUTHOR]

Kogia sima and Kogia breviceps are apex predators of mesopelagic trophic webs being far from most anthropogenic threats. However, chemical pollutants and naturally synthesized compounds may travel long distances. This study aimed to use kogiid whales as sentinels of mesopelagic trophic webs in the Southwestern Atlantic Ocean. Persistent organic pollutants (POPs), e.g., polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and metabolites, mirex, hexachlorobenzene (HCB), polybrominated diphenylethers (PBDEs), pentabromoethylbenzene (PBEB) and hexabromobenzene (HBB), and the naturally produced methoxylated BDE (MeO-BDEs) were determined in the blubber of 16 K. sima and 15 K. breviceps. Among the organochlorine compounds, DDTs were the main group found in K. sima and in K. breviceps (1636.6 and 3983.3 ng g−1 lw, respective medians), followed by PCBs (425.9 and 956.1 ng g−1 lw, respectively), mirex (184.1 and 375.6 ng g−1 lw, respectively), and HCB (132.4 and 340.3 ng g−1 lw, respectively). As for the organobromine, the natural MeO-BDEs were predominant (1676.7 and 501.6 ng g−1 lw, respectively), followed by PBDEs (13.6 and 10.3 ng g−1 lw, respectively) and PBEB (2.2 and 2.9 ng g−1 lw, respectively). In general, POPs concentration was higher in K. breviceps than in K. sima. Conversely, MeO-BDEs concentration was higher in K. sima than in K. breviceps. Differences in concentrations in these sympatric odontocetes were attributed to distinct species, sampling sites, and biological parameters and suggest some level of niche segregation. It is noteworthy the long-range reach and bioaccumulation of these synthetic compounds in an unexplored habitat, that present an increasing economic interest. [Display omitted] • The mesopelagic Kogia sima and K. breviceps can be sentinels of deep-water habitats. • DDTs were the main group of organochlorines and MeO-BDEs of organobromines detected. • PBEB, an emergent pollutant, was detected in these mesopelagic predators. • K. sima presents higher concentration of natural and K. breviceps of synthetic compounds. • Differences in the profile suggest niche segregation in these sympatric species. [ABSTRACT FROM AUTHOR]