Avian blood and feathers as biological tools to track impacts from trace-metals: Bioaccumulation data from the biggest environmental disaster in Brazilian history.

The Mariana's dam collapse was the worst environmental disaster in Brazilian history and one of the biggest worldwide. This perverse disaster resulted in the release of a contaminated mud tsunami that greatly impacted both aquatic and terrestrial biota. The aim of this study was to track environmental impacts resulting from Mariana's disaster using trace-element accumulation in avian blood and feathers as monitoring tool. For this, animals were collected at Doce River mouth (Regência), origin of the contaminated mud, and at southern (Aracruz) and northern (São Mateus) coastal areas. There were two sampling events (2018-2019), one during the winter period (first collection) and another during the summer period (second collection). Trace-element assessed were As, Cd, Cr, Cu, Fe, Pb, Hg, Mn and Zn. Findings show that inorganic contamination in birds followed a strong spatial and temporal behavior. In terms of time patterns, blood and feather contamination levels were markedly elevated in samples from the first collection event in comparison to the second. In terms of space, bioaccumulation was greater in Doce River mouth (Regência) and southern area (Aracruz). Additionally, levels found for Pb, Hg, As and Cd in birds from the first expedition were above proposed threshold levels, indicating possible health impacts. Finally, it is concluded that avian from areas impacted by Mariana's disaster still presents elevated levels of inorganic contamination even after 5 years following the event. Additionally, local climatic factors might pose as major drivers for bioaccumulation patterns in these animals, resulting in marked spatial and temporal fluctuations.

Mechanisms of copper accumulation in isolated mantle cells of the marine clam Mesodesma mactroides.

In vivo copper accumulation was determined in tissues (mantle, gills, digestive gland, and hemolymph) following exposure to Cu (5 µM) for up to 96 h. Mantle was the tissue that accumulated the most Cu, followed by gill, digestive gland, and hemolymph. Therefore, in vitro Cu accumulation was evaluated in isolated mantle cells exposed to 0.5, 1.0, 2.5, and 5.0 µM Cu for 1 and 3 h. After both exposure times, no change in cell viability was observed. However, a significant Cu accumulation was observed in cells exposed to 2.5 and 5.0 µM Cu. Cell exposure to 2.5 µM Cu for 1 h did not affect the ionic (Na(+), K(+), Ca(2+), and Cl(-)) content of isolated mantle cells, characterizing an "ideal" noneffect concentration for the study of the involvement of different ion-transporting proteins (Na(+), K(+), and Cl(-) channels; Na(+)/K(+) 2Cl(-) and Na(+)/Cl(-) cotransporters; Na(+)/Ca(2+), Cl(-)/HCO3-, and Na(+)/H(+) exchangers; Na(+)/K(+) -ATPase; V-ATPase; and carbonic anhydrase) in Cu accumulation. Isolated cells were pre-exposed (30 min) to specific blockers or inhibitors of the ion-transporting proteins and then exposed (1 h) to Cu (2.5 µM) in the presence of the drug. A significant increase of 29.1 and 24.3% in Cu accumulation was observed after cell incubation with acetozalamide (carbonic anhydrase inhibitor) and NPPB (Cl(-) channels blocker), respectively. On the other hand, a significant decrease (48.2%) in Cu accumulation was observed after incubation with furosemide (Na(+) /K(+)/2Cl(-) blocker). Taken together, these findings indicate the mantle as an important route of Cu entry in M. mactroides, pointing to the cotransporter Na(+)/K(+)/2Cl(-) as a major mechanism of Cu accumulation in mantle cells of the clam.

Effect of copper on ion content in isolated mantle cells of the marine clam Mesodesma mactroides.

The effect of copper on ion content (Na(+), K(+), Ca(2+), and Cl(-)) was evaluated in isolated mantle gills of the marine clam Mesodesma mactroides. Clams were collected at the Mar Grosso Beach (São José do Norte, Rio Grande do Sul [RS], southern Brazil), cryoanesthetized, and had their mantles dissected. Mantle cells were isolated and incubated in a calcium-free phosphate solution without (control) or with Cu (CuCl(2)). Cells were exposed to Cu for 1 h (5 µM) or 3 h (2.5 and 5 µM). In cells incubated with 2.5 µM Cu, a significant decrease in intracellular Cl(-) content was observed. However, in cells incubated with 5.0 µM Cu, significant reductions in Na(+), K(+), and Cl(-) intracellular content were observed. Given the mechanisms involved in ion transport in mantle cells of the marine clam M. mactroides, the findings described here suggest that Cu exposure inhibits carbonic anhydrase and Na(+)/K(+) -ATPase activity. Also, it can be suggested that Cu is competing with Na(+) for the same mechanisms of ion transport in the cell membrane, such as the Na(+) channels and the Na(+)/K(+)/2Cl(-) cotransporter. Results from the present study also clearly indicate that processes involved in cellular anion regulation are more sensitive to Cu exposure than those associated with the cellular cation regulation. Characterization of sites for Cu accumulation and toxicity in aquatic animals is important for derivation of metal binding constants at the biotic ligand. Also, identification of the mechanism of metal toxicity is needed for modeling metal accumulation in the biotic ligand and its consequent toxicity. Therefore, the findings reported here are extremely valuable for the development of a biotic ligand model version for marine and estuarine waters.