MEPS 166:259-265 (1998)  -  doi:10.3354/meps166259

Relationship between mercury levels and diet in Azores seabirds

L. R. Monteiro1,*, J. P. Granadeiro2,3, R. W. Furness3

1Departamento de Oceanografia e Pescas, Universidade dos Açores, P-9900 Horta, Portugal 2Instituto da Conservação da Natureza, Rua Filipe Folque 46, 3º, P-1050 Lisboa, Portugal 3Ornithology Group, Institute of Biomedical and Life Sciences, Graham Kerr Building, University of Glasgow, Glasgow G12 8QQ, United Kingdom

Mercury concentrations were determined in feather and food samples from adults of 6 seabird species from the Azores archipelago. Mean concentrations ranged from 54 to 432 ng g-1 dry weight in food and 2.1 to 22.3 µg g-1 fresh weight in feather samples and were highly significantly and positively correlated. Significant seasonal differences in dietary mercury were also registered. Both feather and food mean concentrations were 4-fold higher in seabirds feeding on mesopelagic prey than in those feeding predominantly on epipelagic prey. Concentrations in feathers were 150x those in food, which represents the highest methylmercury biomagnification factor reported for consumers in aquatic foodchains. These findings show that the inclusion of mesopelagic prey in seabird diet has an influence on mercury accumulation over and above that from trophic status and emphasises further the value of seabird feathers as monitors of the ecological hazards of mercury in marine ecosystems.


Mercury · Seabirds · Diet · Feathers · Biomagnification · Monitoring


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