High-precision isotopic analysis sheds new light on mercury metabolism in long-finned pilot whales (Globicephala melas)

• Published in: Scientific Reports
• Main Authors: Bolea Fernandez, Eduardo, Rua Ibarz, Ana Maria, Krupp, Eva M., Feldmann, Jörg, Vanhaecke, Frank
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2019
• Subjects: Biology and Life Sciences; Multidisciplinary; PHOCA-VITULINA-RICHARDII; PACIFIC HARBOR SEAL; INORGANIC MERCURY; HEAVY-METALS; MARINE MAMMALS; ABIOTIC METHYLATION; STRIPED DOLPHIN; TRACE-ELEMENTS; FOOD WEBS; METHYLMERCURY; Pacific; harbor seal; Phoca vitulina
• Online Access: https://biblio.ugent.be/publication/8660537; http://hdl.handle.net/1854/LU-8660537; https://doi.org/10.1038/s41598-019-43825-z; https://biblio.ugent.be/publication/8660537/file/8661988

Whales accumulate mercury (Hg), but do not seem to show immediate evidence of toxic effects. Analysis of different tissues (liver, kidney, muscle) and biofluids (blood, milk) from a pod of stranded long-finned pilot whales (Globicephala melas) showed accumulation of Hg as a function of age, with a significant decrease in the MeHg fraction. Isotopic analysis revealed remarkable differences between juvenile and adult whales. During the first period of life, Hg in the liver became isotopically lighter (delta Hg-202 decreased) with a strongly decreasing methylmercury (MeHg) fraction. We suggest this is due to preferential demethylation of MeHg with the lighter Hg isotopes and transport of MeHg to less sensitive organs, such as the muscles. Also changes in diet, with high MeHg intake in utero and during lactation, followed by increasing consumption of solid food contribute to this behavior. Interestingly, this trend delta Hg-202 is reversed for livers of adult whales (increasing delta Hg-202 value), accompanied by a progressive decrease of delta Hg-202 in muscle at older ages. These total Hg (THg) isotopic trends suggest changes in the Hg metabolism of the long-finned pilot whales, development of (a) detoxification mechanism(s) (e.g., though the formation of HgSe particles), and Hg redistribution across the different organs.