Compostos organoclorados em golfinho-rotador (Stenella longirostris Gray, 1828) da plataforma externa e talude continental das regiões sudeste e sul do Brasil

Abstract

Organochlorine compounds are ubiquitous pollutants, which possess a great environmental persistence, high toxicity, and wide transport capability. The bioaccumulation patterns for oceanic species and trophic webs far from source areas in the South Atlantic are poorly understood. The present study aimed to evaluate levels and contamination profile of organochlorine compounds (PCBs, DDTs and Mirex) in spinner dolphin (Stenella longirostris) from the outer continental shelf and slope of southeastern and southern regions of Brazil, as well as verify possible geographical and sexual differences. Sampling was performed using the remote biopsy method on oceanographic cruises throughout the study area. Chemical analyzes were performed in 43 subcutaneous adipose tissue according to the methodology adapted from Lailson-Brito et al. (2010). The specimens were grouped considering oceanographic processes of southeast (n = 33) and south (n = 10) regions. Although PCBs represented 50% of the contamination profile of the southeast region, organochlorine pesticides (DDTs and Mirex) were also important, indicating a strong contribution from agricultural and industrial activities in this region. Meanwhile, for the southern region, DDTs were the most representative (68%). The median concentration of PCB for the southeast region was 5437.3 ng/g lip and for the southern region 2159.2 ng/g lip, DDT was 4214.6 ng/g lip in the southeast and 3189 ng/g lip in the south, and Mirex 1273.7 ng/g lip in the southeast and 1392.6 ng/g lip in the south. Significative differences between regions were observed only for PCB. Mirex concentrations are among the highest reported for cetaceans in the region. In PCBs contamination profile, hexachlorinated compounds were predominant, especially the most recalcitrant congeners PCBs 153, 138, and 180. p,p' DDE predominated at DDTs contamination profile, indicating historic contamination. Only Mirex presented significant differences in concentrations between males and females. The discriminant analysis was carried out to assess possible geographical differences in the contamination profile of the individuals collected throughout the study area. Three assemblages (Cabo Frio, RJ/SP, and South Area) were identified, suggesting ecological differences associated with the use of different foraging areas by these individuals. The habitat uses of these groups coincide with higher cetacean’s density areas, and therefore, also shows a high prey density. This result is related to the occurrence of mesoscale oceanographic processes, such as upwellings, presence of eddies, meanders, confluences zone, and the influence of coastal plumes. Therefore, these processes are essential for the increase of local productivity, prey aggregation, development of oceanic trophic webs, and result in different distribution patterns of these contaminants.