Satie Taniguchi

Guiana dolphins ( Sotalia guianensis ) are coastal top predators exposed to persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs). We evaluated PCBs, DDTs, and PAHs in liver tissues of 70 stranded individuals from the Santos Basin, southeastern Brazil. The maximum concentrations reached, in wet weight, 759 ng g⁻ ¹ for total PCBs and 242 ng g⁻ ¹ for total DDTs. Parent PAHs were quantified in 20 samples, predominantly as naphthalene, with concentrations up to 200 ng g⁻ ¹ . This indicates a low hepatic occurrence of the measured parent PAHs but does not necessarily imply low environmental exposure. Descriptively, PCB and DDT concentrations tended to be higher in individuals stranded in Rio de Janeiro and São Paulo than in Paraná and Santa Catarina, although interpretation is limited by the unbalanced sampling design and unknown movement histories. Fetuses generally showed lower PCB concentrations, while calves, juveniles, and adults exhibited substantial variability and overlapping concentration ranges, a pattern consistent with possible age-related accumulation but potentially influenced by other biological and geographic factors. Detection in fetal liver demonstrated prenatal exposure but did not allow maternal transfer to be quantified. Concentrations varied substantially among years between 2017 and 2022, but no consistent temporal trend was evident; annual sample sizes were small and uneven. Despite these limitations, this dataset provides an important regional baseline for future assessments of contaminant exposure in Sotalia guianensis.

Stable isotope analysis is an important tool for investigating trophic ecology and contaminant exposure in marine organisms. This study evaluated the relationship between stable carbon (δ13C) and nitrogen (δ15N) isotopes, biological variables, and persistent organic pollutant (POP) concentrations in juvenile green turtles, Chelonia mydas, stranded along the Santos Basin coast, Brazil. Liver (n = 102) and adipose tissue (n = 48) samples were collected from stranded individuals across Rio de Janeiro, São Paulo, Paraná, and Santa Catarina. Stable isotope analyses were used to investigate trophic ecology, habitat use, environmental variability, and trophic breadth, and the results were correlated with previously reported concentrations of organochlorine pesticides, polychlorinated biphenyls, and polybrominated diphenyl ethers. Significant differences in δ13C and δ15N values were observed between liver and adipose tissues, reflecting distinct metabolic turnover rates. Regional differences were significant for δ13C in both tissues, suggesting spatial variation in habitat use and carbon sources, whereas δ15N values did not differ among regions, indicating similar trophic positions among individuals. Juvenile turtles showed broad isotopic variability, consistent with opportunistic feeding behavior and dietary plasticity during ontogenetic transition. Correlation analyses with POPs revealed significant relationships between isotopic signatures and some contaminants. In liver tissue, heptachlor showed a negative correlation with δ13C, whereas in adipose tissue, hexachlorobenzene (HCB) was positively correlated with δ13C and negatively correlated with δ15N. These findings suggest that habitat use and trophic ecology influence contaminant bioaccumulation in juvenile Chelonia mydas along the Santos Basin coastline.

Two marine sediment cores (MDBT 557 and MDBT 561) from the southern Brazilian shelf were analyzed to reconstruct Holocene variations in terrigenous organic matter (OM) input, vegetation dynamics, and the climatic–oceanographic processes influencing sediment deposition. Using sedimentological, molecular and isotopic proxies we identified site‐specific differences in OM delivery but coherent long‐term regional trends. During the early Holocene, both records indicate low terrigenous input, reflecting a weakened South American Monsoon System (SAMS) over the La Plata River (LPR) basin and reduced continental runoff, which, despite lower relative sea level (RSL), likely limited effective sediment export from the LPR and smaller coastal watersheds. Molecular proxies show that vegetation in southeastern South America was dominated by C ₄ ‐rich grasslands, with minimal forest contribution, consistent with drier regional conditions. In the middle Holocene, weakened monsoon precipitation combined with a sustained RSL highstand restricted sediment dispersal across the shelf, maintaining low terrigenous OM input. Nonetheless, subtle lipid biomarker shifts suggest transitional vegetation states and gradual increases in humidity at the basin margins. A marked change occurs around 6,000 cal BP, when hydrodynamic reorganizations expanded the LPR plume over the shelf, altering the provenance of terrigenous OM. This shift marks the late‐Holocene onset conditions, characterized by increased precipitation driven by strengthening summer insolation, intensification of the SAMS, and the establishment of a modern ENSO‐like regime after ∼4,000 cal BP. Consequently, terrigenous OM input and forest‐derived signatures increased substantially, reflecting the expansion of Araucaria and Atlantic Forest taxa across southeastern South America.

This study evaluated the bioavailability of polycyclic aromatic hydrocarbons (PAHs) in Santos Bay (SB) and the adjacent Santos Continental Shelf (SCS) in Brazil. Biliary metabolites were measured in several fish species to establish a baseline for future monitoring programs. Bile samples from different species of fish were collected monthly from July to December 2005 in SB, and in August 2005 and February 2006 on SCS. Metabolite concentrations were determined using high-performance liquid chromatography with fluorescence detectors. Naphthalene, phenanthrene, and benzo[a]pyrene metabolite concentrations ranged from 24 to 810 µg g ^-1 of bile, 1.8 to 68 µg g ^-1 of bile, and below the limit of quantitation to 1.3 µg g ^-1 of bile, respectively. Despite its high concentrations, the levels of naphthalene metabolites were in regions of low-contamination, while benzo[a]pyrene metabolite were in the same range as those reported in moderately contaminated areas, which may indicate pyrolytic contamination by PAHs. No significant differences in the metabolite concentrations were found between the SB and the SCS samples or during the periods of collection. Future studies with a single biomonitoring species should be conducted, considering age, sex, and feeding condition of the individuals. The metabolite data presented in this study is an important baseline information for this urbanized region, which hosts several sources of contaminants.