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Assessing persistent organic pollutant (POP) levels across regions helps evaluate environmental health and determine ecological risks. As an apex predator, the common dolphin (Delphinus delphis) serves as an excellent model for understanding POP exposure and impact in Eastern North Atlantic marine ecosystems. In this study, we collected biopsy samples of common dolphins in two ecoregions, the pelagic system of Madeira Island (Portugal) (n = 30) and in the continental shelf of Northwest Portugal (n = 14) to analyse organochlorine concentrations (PCBs, DDTs, Mirex, HCB) from their blubber. For both ecoregions, PCBs comprised the largest proportion of the total measured organochlorines (60% in Madeira Island and 85% in Northwest Portugal), followed by DDTs, and lastly, HCB. Considerable differences in the organochlorine profile were identified between samples from Madeira and Northwest Portugal, with common dolphins showing higher PCB loads in Northwest Portugal (53 ± 37 μg g -1 lw) compared to Madeira Island (11 ± 4.8 μg g -1 lw). The high levels of PCBs found in individuals from mainland Portugal - reaching values up to 140 μg g -1 lw - are some of the highest reported for the species worldwide, considerably exceeding toxicity thresholds. This is of particular concern as they may be potentially affecting important physiological processes of the animals. These results highlight the poor habitat quality in one of the studied regions, with potential impacts on ecosystem health, while offering valuable insights into the population structure of a species that remains understudied for effective management and conservation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Organic contaminants with toxic effects, like the conventional brominated flame retardants (BFRs) and BFRs of emergent concern, and their synergistic effects with other micropollutants, can be an additional threat to delphinids. Rough-toothed dolphins (Steno bredanensis) populations strongly associated with coastal environments already face a potential risk of decline due to high exposure to organochlorine pollutants. Moreover, natural organobromine compounds are important indicators of the environment's health. Polybrominated diphenyl ethers (PBDEs), pentabromoethylbenzene (PBEB), hexabromobenzene (HBB) and the methoxylated PBDEs (MeO-BDEs) were determined in the blubber of rough-toothed dolphins from three ecological populations from the Southwestern Atlantic Ocean (Southeastern, Southern and Outer Continental Shelf/Southern populations, SE, S, and OCS/S, respectively). The profile was dominated by the naturally produced MeO-BDEs (mainly 2'-MeO-BDE 68 and 6-MeO-BDE 47), followed by the anthropogenic BFRs PBDEs (mainly BDE 47). Median ΣMeO-BDE concentrations varied between 705.4 and 3346.0 ng g -1 lw among populations and ΣPBDE from 89.4 until 538.0 ng g -1 lw. Concentrations of anthropogenic organobromine compounds (ΣPBDE, BDE 99 and BDE 100) were higher in SE population than in OCS/S, indicating a coast - ocean gradient of contamination. Negative correlations were found between the concentration of the natural compounds and age, suggesting their metabolization and/or biodilution and maternal transference. Conversely, positive correlations were found between the concentrations of BDE 153 and BDE 154 and age, indicating low biotransformation capability of these heavy congeners. The levels of PBDEs found are concerning, particularly for SE population, because they are similar to concentrations known for the onset of endocrine disruption in other marine mammals and may be an additional threat to a population in a hotspot for chemical pollution., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

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%.

Atlantic spotted dolphins were recorded on the coastal area of Rio de Janeiro with equipment of 192 kHz sampling rate. The animals produced an average of 33 whistles/min. The repertoire was balanced among four contour categories, with the occurrence of a stereotyped whistle. Frequency parameters were measured between 1.3 and 29 kHz, which represents an increase in the frequency range previously reported for this species in the southwestern Atlantic Ocean. With the use of a higher sampling rate, the acoustic parameters of S. frontalis whistles have changed significantly and became more similar to those reported for North Atlantic populations.