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The effects of iron, manganese, zinc, copper, and lead on the chlorophyll content, carbon assimilation, and the antiradical activity of Rhizophora mangle and Laguncularia racemosa were evaluated in regions affected by the Fundão dam disruption in Brazil. The mine waste which settled and accumulated in the sediments could represent long-term contamination. It can be expected that the iron oxyhydroxides deposited in the sediments will be solubilized, leading to chronic contamination by trace metals and the accumulation of these metals in the biota. In this sense, biological indicators prove to be important tools to assess this type of damage. The different bioaccumulation of metals by the species revealed that R. mangle was more impacted by Mn and Cu and that L. racemosa showed alterations in its physiological responses in the presence of Cu, Zn, and Fe. The concentration of these metals in the leaves, with values above previous local reference limits, was associated with reductions in the chlorophyll-a and chlorophyll-b content and carbon assimilation, mainly in L. racemosa. The antiradical activity was also altered, suggesting a lower ability of both species to eliminate reactive oxygen species (ROS). A possible reason for the symptoms of oxidative stress may be due to the reduced efficiency of antioxidant defense by Cu2+ and Zn2+. In addition, the presence of Pb in the leaf tissue may be toxic to the fauna and the bioaccumulation of this metal and trace elements can be a way to transfer them into the food web by biomagnification. |
