title: Evidence of mercury biomagnification in the food chain of the cardinal tetra Paracheirodon axelrodi (Osteichthyes: Characidae) in the Rio Negro, central Amazon, Brazil.
abstract: In this study, nitrogen stable isotope (δ(15) N) and total mercury (THg) analyses were conducted on algae, submersed and emergent macrophytes, shrubs and trees, Macrobrachium sp. and Paracheirodon axelrodi collected in three streams that drain a large interfluvial region in the middle Rio Negro, Amazonas State, Brazil. Samples were collected during different hydrological periods over 12 months in lower stream reaches and their headwaters; the latter being characterized by shallow, open-canopy swamps. Additionally, δ(15) N values and mercury concentrations of Paracheirodon simulans and Cichla spp. from the middle Rio Negro were analysed to demonstrate THg biomagnification in the food web. The highest mercury levels of P. axelrodi were found in small individuals, which were collected principally in the low water period. The log10 THg-δ(15) N relationship of vascular plants and algae, Macrobrachium sp., Paracheirodon spp. and Cichla spp. showed significant mercury biomagnification among trophic levels, with regression slopes of 0·15 and 0·25 for the entire food web and heterotrophs-only food web, respectively. The mean ± s.d. THg concentrations for Macrobrachium sp., P. axelrodi, P. simulans and Cichla spp. were 63·6 ± 23·7, 104·5 ± 40·0, 112·3 ± 31·4 and 418·5 ± 188·1 ng g(-1) wet mass, respectively. Elevated levels of mercury found in Paracheirodon spp. and top predators such as Cichla spp. in a remote area far from anthropogenic inputs provide evidence that high mercury concentrations occur naturally in Rio Negro aquatic food webs.
authors.affiliation: Departamento de Ciências Pesqueiras nos Trópicos (CIPET), Faculdade de Ciências Agrárias (FCA), Universidade Federal do Amazonas (UFAM), Av. Gen. Rodrigo Otávio 3000, Japiim, Manaus, AM, 69077-000, Brazil.
authors.forename: B G
authors.initials: BG
authors.lastname: Marshall
authors.affiliation: Coordenação de Pesquisas em Dinâmica Ambiental (CDAM), Instituto Nacional de Pesquisas da Amazônia (INPA), Caixa Postal 478, Manaus, AM, 69011-970, Brazil.
authors.forename: B R
authors.initials: BR
authors.lastname: Forsberg
authors.affiliation: Departamento de Engenharia de Pesca e Aquicultura, Centro de Ciências Agrárias Aplicadas, Universidade Federal de Sergipe, Cidade Universitária Prof. José Aloísio de Campos, São Cristóvão, SE, 49100-000, Brazil.
authors.forename: M
authors.initials: M
authors.lastname: Thomé-Souza
authors.affiliation: Laboratório de Biologia Ambiental, Instituto de Ciências e Tecnologia das Águas (ICTA), Universidade Federal do Oeste do Pará (UFOPA), Av. Marechal Rondon, s/n, Bairro:Caranazal, Santarém, PA, 68040-070, Brazil.
authors.forename: R
authors.initials: R
authors.lastname: Peleja
authors.affiliation: Centre for Nuclear Energy in Agriculture (CENA), University of São Paulo, Piracicaba, SP, 13416-000, Brazil.
authors.forename: M Z
authors.initials: MZ
authors.lastname: Moreira
authors.affiliation: Departamento de Ciências Pesqueiras nos Trópicos (CIPET), Faculdade de Ciências Agrárias (FCA), Universidade Federal do Amazonas (UFAM), Av. Gen. Rodrigo Otávio 3000, Japiim, Manaus, AM, 69077-000, Brazil.
authors.forename: C E C
authors.initials: CE
authors.lastname: Freitas
mesh_terms: D000818:Animals; D001938:Brazil; D060126:Characidae / Q000378:metabolism*; D023681:Cichlids / Q000378:metabolism; D004784:Environmental Monitoring; D005399:Fishes; D020387:Food Chain; D008628:Mercury / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D009587:Nitrogen Isotopes / Q000378:metabolism; D010944:Plants / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D009587:Nitrogen Isotopes; D014874:Water Pollutants, Chemical; D008628:Mercury; D009584:Nitrogen
keywords: THg; blackwater; interfluvial swamps; nitrogen stable isotopes