RESUMO
Mercury (Hg) contamination remains a significant environmental concern. In aquatic ecosystems, Hg can undergo methylation, forming its organic form, methylmercury (MeHg), which bioaccumulates and biomagnifies in the food chain, ultimately reaching the top predators, including waterfowl. The objective of this study was to investigate the distribution and levels of Hg in wing feathers, with a specific focus on evaluating heterogeneity in the primary feathers of two kingfisher species (Megaceryle torquata and Chloroceryle amazona). The concentrations of total Hg (THg) in the primary feathers of C. amazona individuals from the Juruena, Teles Pires, and Paraguay rivers were 4.724 ± 1.600, 4.003 ± 1.532, and 2.800 ± 1.475 µg/kg, respectively. The THg concentrations in the secondary feathers were 4.624 ± 1.718, 3.531 ± 1.361, and 2.779 ± 1.699 µg/kg, respectively. For M. torquata, the THg concentrations in the primary feathers from the Juruena, Teles Pires, and Paraguay rivers were 7.937 ± 3.830, 6.081 ± 2.598, and 4.697 ± 2.585 µg/kg, respectively. The THg concentrations in the secondary feathers were 7.891 ± 3.869, 5.124 ± 2.420, and 4.201 ± 2.176 µg/kg, respectively. The percentage of MeHg in the samples increased during THg recovery, with an average of 95% in primary feathers and 80% in secondary feathers. It is crucial to comprehend the current Hg concentrations in Neotropical birds to mitigate potential toxic effects on these species. Exposure to Hg can lead to reduced reproductive rates and behavioral changes, such as motor incoordination and impaired flight ability, ultimately resulting in population decline among bird populations.
Assuntos
Amazona , Mercúrio , Compostos de Metilmercúrio , Poluentes Químicos da Água , Humanos , Animais , Mercúrio/análise , Ecossistema , Plumas/química , Paraguai , Monitoramento Ambiental , Aves , Poluentes Químicos da Água/análiseRESUMO
Bird species have been widely used as suitable bioindicators of environmental mercury (Hg). However, there is still some debate about the most suitable tissue to indicate Hg body burden in birds. For a long time, blood and feathers have proved to be relevant to monitor Hg at different time scales, and recently, bill sheath has been suggested as a potential tissue to this end. In the present study, we evaluated THg in muscle, liver, feathers, claws, and bill sheath in two waterbird species (i.e. the ringed and the Amazon kingfishers) from the Teles Pires, Juruena and Paraguay rivers. Considering all species and sites, feathers (5.47 ± 2.15 µg/g) and bill sheath (3.39 ± 1.37 µg/g) had mean THg concentrations about 2-, 3- and 10-times higher than claws, liver and muscle, respectively. When bird species were segregated, the ringed kingfisher showed THg values 1.8 times higher than the Amazon kingfisher in all tissues. Moreover, results showed that the Amazon kingfisher from the Juruena and Teles Pires rivers was clearly separated from the Paraguay River (control site), and was associated with higher THg values in the claws and feathers. Results obtained for the THg concentrations in bill sheath, muscle and liver tissues of the Amazon kingfisher using multivariate analysis of canonical variates (CVA) showed a pattern of segregation between the sampling areas, being the highest THg values in Teles Pires River samples. The largest bill sheath vector in the CVA suggests that this tissue is a key variable in the segregation of the samples. Overall, feathers may be useful for effects monitoring or spatial patterns, whereas bill sheath, which are more invasive, may be advantejous for temporal trends and retrospective studies of Hg pollution.
Assuntos
Mercúrio , Poluentes Químicos da Água , Animais , Mercúrio/análise , Monitoramento Ambiental , Monitoramento Biológico , Estudos Retrospectivos , Aves , Poluentes Químicos da Água/análise , PlumasRESUMO
The evaluation of mercury (Hg) toxicity in wildlife species has prompted a search for sensitive indicators to accurately measure the body burden of Hg. Despite the extensive use of feathers as an indicator of Hg in birds, they do not appear to be an entirely suitable indicator of the extent of contamination in certain conditions and bird species since Hg levels are influenced by the growth period, timing of the last moult and migration. This research aimed to evaluate rhamphotheca as a potential indicator of environmental Hg concentrations in seabirds. We used culled yellow-legged gulls (Larus michahellis) (n = 20) and determined THg in rhamphotheca and feathers. We distinguished between upper and lower rhamphotheca, and divided each one into 16 equal portions along the culmen to analyse their THg content spatially. In each bird, THg was also determined in primary (P1) and secondary (S8) feathers and compared with rhamphotheca. The median (25th, 75th percentile) rhamphotheca Hg concentration was 13.44 (9.63, 17.46) µg/g, which was twofold higher than in the feathers 7.56 (4.88, 12.89) µg/g. Median THg in rhamphotheca was significantly higher (p < 0.05) in females 15.05 (10.35, 23.04) µg/g than in males 12.34 (8.57, 15.19) µg/g, whereas no differences (p > 0.05) were found in the feathers. No significant differences in Hg levels were found between upper and lower beak mandibles or along either. In contrast, significant differences in Hg concentrations were found between the P1 and S8 feathers (mean, 12.04 vs. 6.04 µg/g). No correlation was found between Hg content in rhamphotheca and feathers. Mercury levels in rhamphotheca exhibited stronger significant relationships with weight (R2 = 0.568), length (R2 = 0.524) and culmen (R2 = 0.347) than the levels in the feathers, which showed no correlation. Overall, our results suggest that rhamphotheca is a suitable tissue indicator for Hg monitoring in gulls; however, further studies are needed to extend our research to other bird species.