Botos-cinza (Sotalia guianensis) da Baía de Sepetiba – RJ, Brasil: Variação temporal da bioacumulação de compostos organoclorados e sua influência no evento de mortalidade atípica associado ao morbilivírus

Abstract

Organochlorine compounds are persistent organic pollutants capable of causing damage in the immune and endocrine systems, and due to their physical and chemical characteristics they are present in the environment until today. High concentrations of these compounds are related to a greater susceptibility to infectious diseases, and long-lived animals with a high trophic level, like cetacean’s odontocetos, tend to have high concentrations. Therefore, the present study aimed to investigate the bioaccumulation pattern of organochlorine compounds in subcutaneous adipose tissue of 85 Guiana dolphins (Sotalia guianensis) from Sepetiba Bay - RJ before, during and after the unusual mortality event (UME) associated to cetacean morbillivirus, as well as the influence of biological parameters on accumulation, maternal transfer and finally, the temporal variation in the concentrations of organochlorine compounds between the years 2007 and 2019. The concentrations of organochlorine compounds are in lipid based, and ranged from 978.86 - 738827, 55 ng/g ΣPCB; 82.44 - 130385.66 ng/g ΣDDT; <LD - 4555.70 ng/g from Mirex; <LD - 1776.72 ng/g from HCH and <LD - 157.97 ng/g from HCB. The concentrations did not differ between the periods analyzed for immature, mature males (Kruskal-Wallis test, p> 0.05) and mature females (Mann-Whitney test, p> 0.05) for most organochlorine compounds, with the exception of PCB 28, which showed higher concentrations in mature females during UME. The concentrations found for 76% of immature individuals, 100% of mature males and 28% of mature females, exceeded the threshold estimated of ΣPCB capable of causing immunosuppressive effects in marine mammals. The concentrations of organochlorine compounds in mature females of Guiana dolphins were significantly lower (Kruskal-Wallis test, p <0.05) than the concentrations of immature and mature males, and showed significant and negative correlation with age (Spearman, p <0.05), and between immature individuals and mature males there was no significant difference (Kruskal-Wallis test, p> 0.05); however, a significant and positive correlation was observed with the age of the animals (Spearman, p <0.05). From the discriminant function analysis, a significant difference was observed in the accumulation pattern of organochlorine compounds between mature females and mature males. Regarding placental transfer, the major ratio were for p.p’-DDE and p.p’-DDD. For 75% of the neonates the ΣPCB concentrations transferred from the females, mainly during lactation, exceeded the threshold estimated for less calves survival. There was a significant increase (p <0.05) in organochlorine compounds concentrations between the years 2007 to 2019 in the Guiana dolphins, as well as a significant change in the pattern of accumulation of the compounds between the periods analyzed. The results of the present study demonstrated a great threat that the Guiana dolphins’ population of Sepetiba Bay is exposed due to the high concentrations of organochlorine compounds, and it is important to develop conservation measures to mitigate the impacts caused by contamination in this region.