Razorbills (Alca torda) as bioindicators of mercury pollution in the southwestern Mediterranean

Levels of mercury (Hg) were analyzed in the tissues of 50 Razorbills (Alca torda), from the Mediterranean area, which had drowned in fishing nets. The mercury distribution pattern in tissues was similar to those of other studies (liver > feather vane > kidney > muscle > brain > feather shaft), with mercury concentrations of 2.85 ± 0.90, 2.66 ± 1.60, 2.23 ± 0.87, 1.54 ± 0.54, 1.48 ± 0.54 and 1.30 ± 0.76 mg/kg (dry weight), respectively. It could be considered that Razorbills in the southwestern Mediterranean were chronically exposed to relatively low levels of MeHg, probably below 0.5 ppm, via dietary intake. We have proposed prediction equations for brain and kidney Hg concentrations using feather shafts as non-invasive samples. This work provides a solid understanding of Razorbill Hg exposure both in their wintering and breeding grounds, and shows that this species can be useful for assessing marine environmental health in the Mediterranean area.