Metal and metalloid contamination and associations with oxidative stress biomarkers in five seabird species sampled off the southeastern Brazilian coast.

Assessing contaminant burdens in seabirds provides valuable insights into environmental quality and species-specific exposure patterns. This study quantified total As, Cd, Cu, Fe, Hg, Pb, Rb, Se, Ti, and Zn, along with two oxidative stress biomarkers involved in metal detoxification, metallothionein (MT) and reduced glutathione (GSH), in the liver and muscle of five seabird species (Spheniscus magellanicus, Sula leucogaster, Fregata magnificens, Larus dominicanus, and Thalasseus maximus) from southeastern Brazil. Metal concentrations were determined via ICP-MS, and biomarkers via UV-Vis spectrophotometry in 56 muscle and 36 liver samples. Liver generally presented higher levels of Cd, Cu, Fe, Hg, Se, Ti, and Zn. Overall, As, Cd, Fe, Hg, Rb, and Se were higher in S. magellanicus and S. leucogaster. Although MT and GSH did not differ among species, both were significantly higher in liver than muscle. Significant correlations were observed between As, Cd, and Ti with GSH, between Cd, Cu, Fe, Rb, and between Ti and MT. Similar levels of Cu, Fe, and Zn across species, values below toxicity thresholds, and correlations with MT suggest metabolic regulation of these metals. Mercury detoxification is primarily associated with Se rather than MT or GSH. Low Pb levels and interspecific differences in As highlight the need for further research, including As speciation analyses and the investigation of Ti sources and biomagnification. Moreover, Ti and Rb showed significant effects in the response of MT and GSH in S. magellanicus and S. Leucogaster. Overall, this study reveals important interspecific variation and antioxidant responses in seabirds, emphasizing key knowledge gaps for future assessments.