Bioacumulação de poluentes orgânicos persistentes em golfinhos-de-dentes-rugosos, Steno bredanensis, das regiões sudeste e sul do Brasil

Abstract

Persistent organic pollutants (POPs) present a specific set of physical-chemical properties that guarantees their persistence in the environment. They can bioaccumulate in marine biota and undergo biomagnification in trophic webs, reaching high concentrations in apex predators. Usually, cetaceans’ coastal populations tend to be more susceptible to these micropollutants and despite being considered an oceanic species, the rough-toothed dolphin (Steno bredanensis) inhabits the Brazilian coast. Therefore, this study aimed to access POPs concentrations in rough-toothed dolphins from south and southeastern regions of Brazil, as well as identify possible differences in bioaccumulation profile between the study sites and determine the influence of biological parameters in the bioaccumulation pattern of POPs in this species. Blubber of stranded or incidentally caught individuals and remote biopsies were collected in the states of Rio de Janeiro (RJ) (n= 19), Paraná (PR) (n= 2), Rio Grande do Sul (RS) (n=2) and at the continental shelf of RS (PCE/RS) (n= 5). Analyses of 28 PCB congeners (ΣPCB), p.p’-DDT and its metabolites p.p’-DDE e p.p’-DDD (ΣDDT), mirex, HCB and α-, β-, γ-HCH isomers (ΣHCH) were performed. Tissue samples underwent organic extraction, followed by acidic clean up and elution in aluminum oxide column. Organochlorine compounds were analyzed in a gas chromatographer coupled to a mass spectrometer in electron impact mode. ΣPCB was predominant in the rough-toothed dolphin contamination profile, followed by ΣDDT, mirex, HCB and HCH. Median concentrations are expressed in μg.g-1lipid weight (μg.g-1lip.). ΣPCB was found at 171. 2 in RJ, 153.3 in PR, 48.7 in RS and 188.5 at PCE/RS. ΣDDT was 25.2 in RJ, 100.9 in PR, 18.6 in RS and 16.3 at PCE/RS. Mirex was 1.8 in RJ, 4.8 in PR, 2.3 in RS and 1.6 at PCE/RS. And HCB was 0.1 in RJ, 0.2 in PR, 0.3 in RS and was not detected at the PCE/RS. ΣHCH was only detected in two individuals. Median concentrations of ΣPCB in all study sites were beyond the 40 μg.g-1lip. limit proposed to start effects in endocrine and immune systems. p.p’-DDE was the main form in the ΣDDT suggesting historical contamination by DDT in the Brazilian coast. ΣDDT/ΣPCB ratio show a predominance of industrial activities and increased population density over agricultural activities. Coastal and continental shelf populations of rough-toothed dolphins were distinguished based on differences in the bioaccumulation profile of POPs. Moreover, biological parameters such as sex, sexual maturity and age showed influence in the bioaccumulation pattern of POPs in rough-toothed dolphins. Adult males presented higher concentrations of POPs than immatures and adult females, due to long-term accumulation whereas adult females transfer part of their pollutants’ load to the offspring. POPs concentrations presented in this study are the highest ever reported for this species all over the world as well as for other species of delphinids from Brazilian coast. The orders of magnitude of POPs in this study are comparable to those of killer whales (Orcinus orca) which are currently on population collapse due to high concentrations of PCBs.