Mercury exposure in relation to foraging ecology and its impact on the oxidative status of an endangered seabird

• Published in: The Science of the total environment 2020-07, Vol.724, p.138131, Article 138131
• Main Authors: Soldatini, Cecilia, Sebastiano, Manrico, Albores-Barajas, Yuri V., Abdelgawad, Hamada, Bustamante, Paco, Costantini, David
• Format: Article
• Language: English
• Subjects: Baja California peninsula; Black-vented shearwater; Ecotoxicology; Life Sciences; Mercury; Pacific Ocean; Stable isotopes; Toxicology
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.138131

Mercury is a natural element extensively found in the Earth's crust, released to the atmosphere and waters by natural processes. Since the industrial revolution, atmospheric deposition of Hg showed a three-to-five-fold enrichment due to human activities. Marine top predators such as seabirds are recognized valuable bioindicators of ocean health and sensitive victims of Hg toxic effects. Hg negatively affects almost any aspect of avian physiology; thus, birds prove valuable to study the effect of Hg exposure in vertebrates. The Black-vented Shearwater is endemic to the North-Eastern Pacific Ocean, where it forages along the Baja California Peninsula during the breeding period. The area has no industrial settlement and is in the southern portion of the California Current System (CCS). After observing possible contamination effects in eggshells, we decided to quantify the exposure of breeding birds to Hg and test for possible effects on oxidative status of the species. The concentration of Hg in erythrocytes averaged 1.84 μg/g dw and varied from 1.41 to 2.40 μg/g dw. Males and females had similar Hg concentrations. The individual trophic level (reflected by δ15N) did not explain Hg exposure. In contrast, individuals foraging inshore had higher Hg concentrations than those foraging more offshore (reflected by δ13C). Shearwaters having higher concentrations of Hg had lower activity of the antioxidant enzyme glutathione peroxidase and showed lower non-enzymatic antioxidant capacity. Levels of plasma oxidative damage, superoxide dismutase and catalase were not associated with Hg. Our results indicate that (i) the foraging habitat is the factor explaining Hg exposure and (ii) there is some evidence for potential harmful effects of Hg exposure to this seabird species of conservation concern. The foraging habitat is the factor explaining Hg exposure in seabirds and we observed potential harmful effects of Hg exposure in a seabird species of conservation concern. [Display omitted] •We quantified the blood Hg concentrations of adult black-vented shearwaters.•Hg concentrations were moderate and similar between sexes.•The foraging habitat explained variation in Hg among birds.•The individual trophic level did not explain Hg exposure.•Hg concentration was negatively correlated with blood antioxidants.