title: Dry season limnological conditions and basin geology exhibit complex relationships with δ13C and δ15N of carbon sources in four Neotropical floodplains.
abstract: Studies in freshwater ecosystems are seeking to improve understanding of carbon flow in food webs and stable isotopes have been influential in this work. However, variation in isotopic values of basal production sources could either be an asset or a hindrance depending on study objectives. We assessed the potential for basin geology and local limnological conditions to predict stable carbon and nitrogen isotope values of six carbon sources at multiple locations in four Neotropical floodplain ecosystems (Paraná, Pantanal, Araguaia, and Amazon). Limnological conditions exhibited greater variation within than among systems. δ15N differed among basins for most carbon sources, but δ13C did not (though high within-basin variability for periphyton, phytoplankton and particulate organic carbon was observed). Although δ13C and δ15N values exhibited significant correlations with some limnological factors within and among basins, those relationships differed among carbon sources. Regression trees for both carbon and nitrogen isotopes for all sources depicted complex and in some cases nested relationships, and only very limited similarity was observed among trees for different carbon sources. Although limnological conditions predicted variation in isotope values of carbon sources, we suggest the resulting models were too complex to enable mathematical corrections of source isotope values among sites based on these parameters. The importance of local conditions in determining variation in source isotope values suggest that isotopes may be useful for examining habitat use, dispersal and patch dynamics within heterogeneous floodplain ecosystems, but spatial variability in isotope values needs to be explicitly considered when testing ecosystem models of carbon flow in these systems.
authors.affiliation: Programa de Pós-Graduação em Ecologia de Ambientes Aquáticos Continentais (PEA), Universidade Estadual de Maringá, Maringá, Paraná, Brasil.|Postdoctoral fellowship, National Council for Scientific and Technological Development (CNPq), Brasília, Distrito Federal, Brasil.
authors.forename: Gustavo H
authors.identifier: http://orcid.org/0000-0002-9233-2824
authors.initials: GH
authors.lastname: Zaia Alves
authors.affiliation: Department of Biological Sciences and the Advanced Environmental Research Institute, University of North Texas, Denton, Texas, United States of America.
authors.forename: David J
authors.initials: DJ
authors.lastname: Hoeinghaus
authors.affiliation: Programa de Pós-Graduação em Biologia Comparada (PGB), Universidade Estadual de Maringá, Maringá, Paraná, Brasil.
authors.forename: Gislaine I
authors.initials: GI
authors.lastname: Manetta
authors.affiliation: Programa de Pós-Graduação em Ecologia de Ambientes Aquáticos Continentais (PEA), Universidade Estadual de Maringá, Maringá, Paraná, Brasil.|Programa de Pós-Graduação em Biologia Comparada (PGB), Universidade Estadual de Maringá, Maringá, Paraná, Brasil.
authors.forename: Evanilde
authors.initials: E
authors.lastname: Benedito
mesh_terms: D002244:Carbon / Q000737:chemistry* / Q000378:metabolism; D002250:Carbon Radioisotopes / Q000737:chemistry / Q000378:metabolism; D017753:Ecosystem; D020387:Food Chain; D005618:Fresh Water; D007554:Isotopes / Q000737:chemistry; D060106:Lakes; D055994:Limnology; D009590:Nitrogen Radioisotopes / Q000737:chemistry / Q000378:metabolism; D010839:Phytoplankton / Q000737:chemistry* / Q000378:metabolism; D045483:Rivers; D012621:Seasons
chemical_list: D002250:Carbon Radioisotopes; D007554:Isotopes; D009590:Nitrogen Radioisotopes; D002244:Carbon