title: Isotopic variation in five species of stream fishes under the influence of different land uses.
abstract: The aim of this study was to test if changes in land use alter the isotopic signature of fish species, promoting changes in the trophic position and food resource partitioning between these consumers. Three different systems were investigated: pasture streams (n = 3), streams in sugar cane plantations (n = 3) and reference streams (n = 3). Fish species Aspidoras fuscoguttatus, Astyanax altiparanae, Characidium zebra, Hisonotus piracanjuba and Knodus moenkhausii were selected, and their nitrogen and carbon isotopic compositions were estimated to assess changes in the trophic level and partitioning of food items consumed. The composition of δ(13) C (‰) only differed among the land use categories for A. altiparanae, H. piracanjuba and K. moenkhausii. Resource partitioning was different for all species, with changes in the sources or proportions they consumed in each land use category, but only A. altiparanae introduced new food sources in large quantity in altered land uses. It is important to note, however, that the results from the resource partitioning analysis are limited due to large overlapping of isotopic signatures between the analysed food resources. All fish species exhibited variation in δ(15) N (‰), with the highest values found in streams under sugar cane or pasture influence. Despite the variation in nitrogen isotopic values, only C. zebra and H. piracanjuba displayed changes in trophic level. Therefore, it is believed that the increase in the δ(15) N (‰) value of the individuals collected in streams under the influence of sugar cane or pasture was due to the greater influence of livestock dung and chemical and organic fertilizers. The results also highlight the importance of studying consumer species along with all forms of resources available at each location separately, because the signatures of these resources also vary within different land uses.
authors.affiliation: Laboratório de Ecologia de Peixes, Setor de Ecologia, Departamento de Biologia, Universidade Federal de Lavras, Campus Universitário, Caixa Postal 3037, CEP 37200-000, Lavras, MG, Brazil.
authors.forename: D R
authors.initials: DR
authors.lastname: Carvalho
authors.affiliation: Laboratório de Ecologia de Bentos, Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, Caixa Postal 486, Pampulha, CEP 30161-970, Belo Horizonte, MG, Brazil.
authors.forename: D
authors.initials: D
authors.lastname: Castro
authors.affiliation: Laboratório de Ecologia de Bentos, Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, Caixa Postal 486, Pampulha, CEP 30161-970, Belo Horizonte, MG, Brazil.
authors.forename: M
authors.initials: M
authors.lastname: Callisto
authors.affiliation: Laboratório de Ecologia Isotópica, Centro de Energia Nuclear na Agricultura - CENA, Universidade de São Paulo, Av. Centenário, 303, Caixa Postal 96, CEP 13400-970, Piracicaba, SP, Brazil.
authors.forename: M Z
authors.initials: MZ
authors.lastname: Moreira
authors.affiliation: Laboratório de Ecologia de Peixes, Setor de Ecologia, Departamento de Biologia, Universidade Federal de Lavras, Campus Universitário, Caixa Postal 3037, CEP 37200-000, Lavras, MG, Brazil.
authors.forename: P S
authors.initials: PS
authors.lastname: Pompeu
mesh_terms: D000383:Agriculture; D000818:Animals; D002244:Carbon; D002247:Carbon Isotopes / Q000032:analysis*; D005308:Fertilizers; D005399:Fishes; D020387:Food Chain; D008372:Manure; D009584:Nitrogen; D009587:Nitrogen Isotopes / Q000032:analysis*; D045483:Rivers; D031786:Saccharum
chemical_list: D002247:Carbon Isotopes; D005308:Fertilizers; D008372:Manure; D009587:Nitrogen Isotopes; D002244:Carbon; D009584:Nitrogen
keywords: carbon; food resources; nitrogen; stable isotopes; trophic position; trophic webs