Monitoring of mercury in the mesopelagic domain of the Pacific and Atlantic oceans using body feathers of Bulwer's petrel as a bioindicator.


Furtado R(1), Granadeiro JP(2), Gatt MC(2), Rounds R(3), Horikoshi K(4), Paiva VH(5), Menezes D(6), Pereira E(7), Catry P(8).
Author information:
(1)MARE - Marine and Environmental Sciences Centre, ISPA - Instituto Universitário, Rua Jardim do Tabaco, 1149-041 Lisboa, Portugal. Electronic address: [Email]
(2)CESAM - Centre for Environmental and Marine Studies, Departamento de Biologia Animal, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal.
(3)Pacific Islands Refuges and Monuments Office Inventory and Monitoring Program U.S. Fish and Wildlife Service, Honolulu, HI 808-792-9559, United States of America.
(4)Institute of Boninology Chichijima, Ogasawara-mura, Tokyo 100-2101, Japan.
(5)Universidade de Coimbra, MARE - Marine and Environmental Sciences Centre, Departamento de Ciências da Vida, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal.
(6)Instituto das Florestas e Conservação da Natureza, IP-RAM, 9064-512 Funchal, Portugal.
(7)Department of Chemistry and CESAM/REQUIMTE, University of Aveiro, 3810-193 Aveiro, Portugal.
(8)MARE - Marine and Environmental Sciences Centre, ISPA - Instituto Universitário, Rua Jardim do Tabaco, 1149-041 Lisboa, Portugal.


Global mercury pollution has markedly and consistently grown over the past 70 years (although with regional variations in trends) and is a source of major concern. Mercury contamination is particularly prevalent in biota of the mesopelagic layers of the open ocean, but these realms are little studied, and we lack a large scale picture of contamination in living organisms of this region. The Bulwer's petrel Bulweria bulwerii, a species of migratory seabird, is a highly specialised predator of mesopelagic fish and squid, and therefore can be used as a bioindicator for the mesopelagic domain. Mercury accumulated by the birds through diet is excreted into feathers during the moulting process in adults and feather growth in chicks, reflecting contamination in the non-breeding and breeding periods, respectively, and hence the influence of different, largely non-overlapping breeding and non-breeding ranges. We studied mercury in feathers and the trophic position in two colonies from the Atlantic Ocean (Portugal and Cape Verde) and two colonies from the Pacific Ocean (Japan and Hawaii). We found significantly lower levels of mercury in adult and chick samples from the Pacific Ocean compared with samples from the Atlantic Ocean. However, we did not detect differences in trophic position of chicks among colonies and oceans, suggesting that differences in mercury measured in feathers reflect levels of environmental contamination, rather than differences in the structure of the trophic chain in different oceans. We conclude that despite a reduction in mercury levels in the Atlantic in recent decades, mesopelagic organisms in this ocean remain more heavily contaminated than in the Pacific at tropical and subtropical latitudes. We suggest that Bulwer's petrel is a highly suitable species to monitor the global contamination of mercury in the mesopelagic domain.