Genotoxicity effects on Geophagus brasiliensis fish exposed to Doce River water after the environmental disaster in the city of Mariana, MG, Brazil

Abstract The Doce River basin has suffered the largest environmental accident ever occurred in Brazil with the influx of tailings from Fundão and Santarém, belonging to Samarco mining company, due to the disaster in Mariana. A spill between 50 and 60 million m3 of tailings was estimated by the company. According to Samarco, the wastewater was composed mainly of clay, silt and heavy metals like iron, copper and manganese. Thereby, the objective of the present study was evaluated the genotoxic damage in juvenile of Geophagus brasiliensis (Quoy e Gaimard, 1824) exposed to Doce river water before (DRWBA – Doce River water before acident) and after (DRWAA – Doce River water after acident) the influx of tailings from the Germano and Santarém Dam disasters in Mariana, MG, Brazil. For this, 24 individuals of the species G. brasiliensis (obtained on IFES/ALEGRE fish culture) were submitted to a bioassay with three treatments and eight replicates. The treatments were: 1) Control water (water from the urban water supply system, filtered with a 0.45 µm membrane), 2) DRBA and 3) DRAA. After 96 h, these fishes were anesthetized to remove blood for evaluation of genotoxic damage (micronucleus and comet). For the bioassay, a total of 80 L of The Doce River water were collected before the influx of tailings and after the influx and then submitted to metal quantification analysis. Fish exposed to DRWBA and DRWAA treatments showed a significant increase in both the number of erythrocyte micronuclei and the DNA damage index in relation to the control fish; however, they did not present any differences between the two treatments. The results demonstrate that the DRWBA treatment was already genotoxic for the fish, mainly due to dissolved Cu concentrations in the water. The DRWAA treatment probably presented genotoxicity due to the increase in the dissolved fraction and synergistic effects of several metals found in the tailings of the Mariana accident.摘要 多西河（Doce River）流域曾遭遇巴西史上最严重的环境事故：萨马科（Samarco）矿业公司所属的丰当（Fundão）与圣塔伦（Santarém）尾矿坝因马里亚纳矿难发生溃坝，大量尾矿涌入流域。据该公司估算，此次溃坝泄漏的尾矿体积达5000万至6000万立方米。萨马科称，泄漏的废水主要由黏土、粉砂以及铁、铜、锰等重金属组成。 本研究旨在评估暴露于巴西米纳斯吉拉斯州马里亚纳市格曼诺（Germano）与圣塔伦坝灾尾矿涌入前（DRWBA——事故前多西河水）、涌入后（DRWAA——事故后多西河水）的多西河水的巴西珠母丽鱼（Geophagus brasiliensis，Quoy & Gaimard, 1824）幼鱼的遗传毒性损伤。 为此，研究人员从IFES/ALEGRE鱼类养殖场获取24尾该种鱼类，设置3组处理、8次重复开展生物检测。处理组分别为：1）对照水（经0.45 μm滤膜过滤的市政供水）、2）DRWBA组与3）DRWAA组。暴露96小时后，将这些鱼麻醉并采集血液，以评估遗传毒性损伤（微核与彗星试验）。 本次生物检测共采集事故前与事故后的多西河水总计80升，用于重金属定量分析。 实验结果显示，相较于对照组，暴露于DRWBA与DRWAA组的鱼类，其红细胞微核数量与DNA损伤指数均显著升高，但DRWBA与DRWAA两组之间未表现出显著差异。研究结果表明，DRWBA组水体已对鱼类产生遗传毒性，这主要与水体中溶解态铜的浓度相关。而DRWAA组的遗传毒性则可能源于尾矿中多种重金属溶解组分的增加及其协同效应。