Potential adverse effects of heavy metals on clinical health parameters of Caretta caretta from a nesting area affected by mining tailings in Brazil

Abstract

BackgroundIn 2015, Brazil had its most notorious ecological disaster due to an iron mine dam collapse. It was considered the world's largest environmental disaster associated with mining industry. The tailings composed mostly of iron ore and silica, but with high levels of heavy metals reached the Atlantic Ocean, through the Doce River, sixteen days after the rupture. The region where the mud ran into the ocean is an important nesting area for loggerhead turtles (Caretta caretta) in Brazil (Povoação, Espírito Santo state). The aim of this study is to evaluate the heavy metal effects on the health parameters of loggerhead turtles that nest in the exposed area (Povoação, Doce river estuary) and compare them with turtles from another coastal area that was not affected by the tailings (Praia do Forte, Bahia state). MethodsAnimals’ health status was determined by a physical examination during which blood samples used to perform biochemical and hematological analysis were also obtained. Heavy metal concentrations were evaluated in the blood and carapace scutes. ResultsSea turtles from Povoação had a worse body condition with higher ectoparasitic and epibiont loads compared to Praia do Forte animals. They also showed eye lesions and more frequent fibropapillomatosis suggestive tumors. Several correlations between the contaminants and hematological and plasma biochemical analytes were found in loggerhead sea turtles from Povoação. Blood metal concentrations were distinct between nesting areas, with higher As, Cd, Cr, Fe, Pb, and Zn levels in animals from the affected area. In the carapace scute, the heavy metal levels were similar between sites. ConclusionThe occurrence of eye lesions, suggestive fibropapillomatosis tumors, worse body condition, higher ectoparasite count, greater epibiont loads, large number of correlations between health parameters and heavy metal levels, and higher levels of some metals in the blood of PV turtles indicates that the tailings could have a negative impact on the health and reproduction of these turtles. The long-term monitoring of the exposed area is important to quantify the direct and indirect impacts of the tailings on the health of these animals. Additionally, the data reported here are important for temporal and spatial comparative studies in the future.