Institute of Biosciences, São Paulo State University, São Vicente, Brazil.
Graduation Program in Ecology and Conservation, Federal University of Paraná, Curitiba, Brazil.
Sci Total Environ. 2022 Nov 10;846:157332. doi: 10.1016/j.scitotenv.2022.157332. Epub 2022 Jul 20.
Sediments represent a major sink and also a main source of contaminants to aquatic environments. An environmental disaster from a mining dam breakage in 2015 in South-East Brazil re-suspended complex mixtures of chemicals deposited in the sediment, spreading contaminants along the Doce River Basin (DRB) major river course. While high levels of contaminants in sediment were well described, toxicological effects in aquatic organisms were poorly investigated. Thus, the effects of these potentially toxic chemicals were assessed in the present study through different endpoints (biochemical to populational levels) in fish embryos of the South-American silver catfish exposed to elutriates from different sites of the DRB. Despite no significant mortality observed, our results showed that exposure to the elutriates, especially those from the closest site to the dam collapse, caused higher deformities rates and DNA damage in the fish embryos than in the control group. Multivariate analysis showed that these sublethal effects may be related to the high levels of metals introduced by mining activities, compromising long-term survival and reproduction success. In addition, it was possible to observe the influence of other sources of pollutants along the river. According to our data, the mathematical model simulated a significant impact on the population density at longer-term exposure, for the sites that showed the most prominent toxicity responses. The fish embryo toxicity test proved to be an effective assay to assess the ecotoxicological effects of the pollutants from a major river contaminated by a mining dam collapse and showed that the survival rate per se was not a suitable endpoint to assess the toxicity of the pollutants. As a consequence, we contributed to shed a light on a potential underestimated impact of pollutants in sediments of the DRB on the native organisms at distinct biological levels of organizations.
沉积物是污染物在水生环境中的主要汇和源。2015 年，巴西东南部一座采矿大坝决堤，造成了一场环境灾难，使沉积在其中的复杂化学混合物重新悬浮，污染物沿着多西河流域（DRB）的主要河道扩散。尽管沉积物中污染物的含量很高，但水生生物的毒理学效应却很少被研究。因此，本研究通过暴露于来自 DRB 不同地点的底泥的南美银鲈鱼胚胎的不同终点（生化到种群水平）评估了这些潜在有毒化学物质的影响。尽管没有观察到明显的死亡率，但我们的结果表明，暴露于底泥，特别是那些离大坝坍塌最近的地点，导致鱼胚胎的畸形率和 DNA 损伤高于对照组。多元分析表明，这些亚致死效应可能与采矿活动引入的高浓度金属有关，从而危及长期生存和繁殖成功。此外，还可以观察到河流沿线其他污染源的影响。根据我们的数据，数学模型模拟了在长期暴露下，对表现出最明显毒性反应的地点的种群密度的重大影响。鱼类胚胎毒性试验被证明是一种有效的方法，可用于评估受采矿大坝决堤污染的主要河流中的污染物的生态毒理学效应，并表明存活率本身并不是评估污染物毒性的合适终点。因此，我们的研究结果阐明了沉积物中的污染物对不同生物组织层次的本地生物的潜在低估影响。
