Natural and anthropogenic organic brominated compounds in the southwestern Atlantic ocean: Bioaccumulation in coastal and oceanic dolphin species.

Marine pollution is considered a current driver of change in the oceans and despite the urgency to develop more studies, there is limited information in the southern hemisphere. This study aimed to analyze the levels and profiles of natural (MeO-PBDEs) and anthropogenic (BFRs: PBDEs, HBB, PBEB) organic brominated compounds in adipose tissue of two species of dolphins with different distribution and trophic requirements from the Southwestern Atlantic Ocean; the short-beaked common dolphin (Delphinus delphis) and the Fraser's dolphin (Lagenodelphis hosei). In addition, we aim to investigate maternal transfer and biological pattern relationship (sex, age, sexual maturity) in short-beaked common dolphin bioaccumulation. The levels of both groups of contaminants were in the same order of magnitude as those reported for other marine mammals on both a regional and global scale. BFRs profiles were dominated by BDE 28 and BDE 47 in short-beaked common dolphin and Fraser's dolphin, respectively, whereas 2-MeO-BDE 68 was the most abundant natural compound in both species. Evidence of maternal transfer, temporary increase in BDE 154 levels and no influence of sex, age, or sexual maturity on brominated compound concentration was observed in short-beaked common dolphin. This study fills a gap in the knowledge of the Southwestern Atlantic Ocean providing new information on emerging organic pollutants bioavailability for dolphins and, therefore, for the different trophic webs. In addition, it serves as a baseline for further contamination assessments.

Commerson's dolphin population structure: evidence for female phylopatry and male dispersal.

A key in species conservation is understanding the amount and distribution of genetic diversity and how environmental changes that occurred in the recent past may have influenced current patterns of population structure. Commerson's dolphin, Cephalorhynchus commersonii, has two subspecies, one of which is endemic to South America (C. commersonii commersonii) and little is known about its population genetics. Our objective was to investigate the population genetics of this subspecies throughout its distribution. Using 70 skin samples and information available in GenBank, 308 mitochondrial DNA sequences and 28 species-specific microsatellites were analyzed. The species presented low genetic diversity when compared to other dolphin species, but was consistent with other species within the genus. Strong population structure based on mitochondrial DNA was exhibited throughout its entire distribution, a pattern consistent with female philopatry. However, this pattern was not detected when using microsatellites, suggesting male-mediated gene flow. Demographic tests suggested a population expansion beginning approximately 15,000 years ago, after the Last Glacial Maximum. In a climate change scenario, we recommended considering each sampling location as an independent population management unit in order to evaluate the impact of possible environmental changes on the distribution of genetic information within the species.

Trace elements in trophic webs from South Atlantic: The use of cetaceans as sentinels.

The odontocetes are at the top of the trophic chains, and because they accumulate numerous compounds throughout life, they are considered as bioindicators of ecosystem contamination. This study aimed to analyze the concentrations of trace elements of the short-beak common dolphin (Delphinus delphis) and Fraser's dolphin (Lagenodelphis hosei) from the Southwestern Atlantic Ocean. Regardless of the tissue and the species, the average concentration of silver was the lowest. The highest concentration in the kidney was cadmium, while in the liver it varied between selenium and total mercury according to the species. The bioconcentration process was present in relation with the age and standard length in common dolphins. Additionally, Se-HgT molar ratios differed among species. This study provides new information on the current state of pollution by trace elements in common and Fraser's dolphins in the Southwest Atlantic, and it serves as a complement to the work in tropical waters.

POPs in the South Latin America: Bioaccumulation of DDT, PCB, HCB, HCH and Mirex in blubber of common dolphin (Delphinus delphis) and Fraser's dolphin (Lagenodelphis hosei) from Argentina.

Organic compounds, in particular organochlorines, are highly persistent compounds which accumulate in biotic and abiotic substrates. Marine mammals bioaccumulate and biomagnify persistent organic pollutants (POPs) through diet. ∑PCB (26 PCB congeners), ∑DDT (pp-DDT, pp-DDD, pp-DDE), ∑HCH (α-HCH, ß-HCH, γ-HCH, δ-HCH), HCB and mirex were analyzed from samples of subcutaneous adipose tissue of common dolphins, Delphinus delphis, and Fraser's dolphins, Lagenodelphis hosei, obtained in 1999 and 2012. The aim of this study was to determine the concentrations of POPs to get baseline information on the current state of pollution by these compounds in these two species in South Atlantic. At the same time, to assess concentrations of POPs in relation to age, the total length and sexual maturity in common dolphins. Organochlorine pesticides dominated Fraser's dolphins, DDT being the most abundant, while PCBs were mostly present in common dolphins. In both species, the distributions of isomers or metabolites followed the order: ß-HCH>δ-HCH>γ-HCH>α-HCH and pp-DDE>pp-DDD>pp-DDT. As for ∑PCB, the largest contribution was given by congeners of high molecular weight, particularly by hexa and hepta - CBs. Common dolphins did not show effects on sexual maturity, age and standard length in the concentration of organochlorines. The mean concentrations found in this study are lower compared to those reported in other studies performed in dolphins elsewhere. This study provides new information regarding levels of organochlorines in common dolphins for the Southwestern Atlantic.