Rhamphotheca as a useful indicator of mercury in seabirds

• Published in: The Science of the total environment 2021-02, Vol.754, p.141730-141730, Article 141730
• Main Authors: de Medeiros Costa, Gerlane, Lázaro, Wilkinson L., Sanpera, Carola, Sánchez-Fortún, Moisès, dos Santos Filho, Manoel, Díez, Sergi
• Format: Article
• Language: English
• Subjects: Beak; Feather; Hg exposure; Larus michahellis; Tissue indicator; Yellow-legged gull
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.141730

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) 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. [Display omitted] •Rhamphotheca was shown to be a suitable tissue to indicate Hg body burden in birds.•Mercury concentrations in rhamphotheca were 2-fold > than in P1 and S8 feathers.•All portions of (and along) the upper and lower rhamphotheca had similar Hg values.•Hg in rhamphotheca was highly significantly related to weight, length, and culmen.•Mercury concentrations in rhamphotheca provide insight into long-term Hg exposure.