Temporal trends of trace elements bioaccumulation by a vulnerable cetacean (Pontoporia blainvillei) before and after one of the largest mining disasters worldwide

One of the largest environmental disasters worldwide occurred on November 5th 2015, when the Fundao dam collapsed in Mariana (Minas Gerais State, Southeast Brazil). The tailing mud flooded the Doce River basin and reached the sea in the coast of Espirito Santo State (ES), Southeast Brazil. This coastal region is the habitat of the most isolated population of frandscana dolphins (Pontoporia blainvillei), with the lowest populational census and lowest genetic diversity in Frandscana Management Area la (FMA Ia) - 18 degrees 25'S and 21 degrees 17'S. This study aimed to assess the bioaccumulation of trace-elements (As, Cd, Cu, Fe, Hg, Mn, and Zn) in musde, liver and kidney of frandscana dolphins collected near the Doce River's mouth before (n = 32) and after (n = 19) the tailing mud reached the sea. The Generalized Additive Model (GAM) showed increasing temporal trends of Hg and Zn in musde and liver after the dam failure, probably related to higher concentrations and bioavailability in the water column and sediments from the Doce River. Declining trends were found for As and Cu muscular and hepatic concentrations and Fe concentrations in kidney due to their lower bioavailability after the disaster, caused by association with tailings mud trapped in the riverbanks and suspended particulate material. Additionally, higher As and Hg concentrations found in the first period of sampling may be due to historical contamination by mining activities. The full extent of the impacts caused by the Fundao dam failure is still unknown. However, due to their rapid increase and remobilization process, toxic effects can be induced in the biota by these elements. Elements' bioaccumulation in this study contributes to the knowledge of franciscana dolphins from FMA Ia. Considering the conservation concern regarding this franciscana population and its scarce knowledge, the impact of this disaster can be alarming for species conservation. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study found that after the collapse of the Fundao dam, there was an increasing trend in mercury and zinc concentrations in the muscle and liver of franciscana dolphins, likely due to higher concentrations and bioavailability in the water column and sediments from the Doce River. Conversely, arsenic and copper in muscle and liver, and iron in kidney showed declining trends, possibly due to lower bioavailability after the disaster. Higher concentrations of arsenic and mercury in the first period of sampling may be attributed to historical contamination from mining activities.