title: Land-use impacts on fatty acid profiles of suspended particulate organic matter along a larger tropical river.
abstract: Land-use change, such as agricultural expansion and urbanization, can affect riverine biological diversity and ecosystem functioning. Identifying the major stressors associated with catchment land-use change is a prerequisite for devising successful river conservation and restoration strategies. Here, we analyzed land-use effects on the fatty acid (FA) composition and concentrations in suspended particulate organic matter (SPOM) along a fourth-order tropical river, the Rio das Mortes. Thereby, we aimed at testing the potential of fatty acids in riverine suspended particulate organic matter (SPOM-FAs) as indicators of land-use change in tropical catchments, and at identifying major human impacts on the biochemical composition of SPOM, which represents an important basal energy and organic matter resource for aquatic consumers. River water SPOM and total FA concentrations ranged between 2.8 and 10.2mg dry weight(DW)L(-1) and between 130.6 and 268.2μg DW L(-1), respectively, in our study. Urbanization was the only land-use category correlating with both FA composition and concentrations, despite its low contribution to whole catchment (1.5-5.6%) and riparian buffer land cover (1.7-6.6%). Higher concentrations of saturated FAs, especially C16:0 and C18:0, which are the main components of domestic sewage, were observed at sampling stations downstream of urban centers, and were highly correlated to urbanization, especially within the 60m riparian buffer zone. Compared to water chemical characteristics (inorganic nutrients, dissolved oxygen, pH, and specific conductance) and river habitat structural integrity, FA variables exhibited a higher variability along the investigated river and were more strongly correlated to urban land use, suggesting that SPOM-FA profiles may be an efficient indicator of urban land-use impacts on larger tropical rivers. High total FA concentrations in the SPOM of urbanized tropical rivers may represent high-energy biochemical subsidies to food webs, potentially leading to changes in functional ecosystem characteristics, such as bacterial and suspension-feeder production.
authors.affiliation: Department of Biosystems Engineering, Federal University of São João del-Rei, Praça Dom Helvécio 74, 36301-160 São João del Rei, MG, Brazil. Electronic address: iboechat@ufsj.edu.br.
authors.forename: I G
authors.initials: IG
authors.lastname: Boëchat
authors.affiliation: Leibniz-Institute of Freshwater Ecology and Inland Fisheries - IGB, Müggelseedamm 301, 12587 Berlin, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Krüger
authors.affiliation: Department of Biosystems Engineering, Federal University of São João del-Rei, Praça Dom Helvécio 74, 36301-160 São João del Rei, MG, Brazil; Graduate Program of Bioengineering, Federal University of São João del-Rei, Praça Dom Helvécio 74, 36301-160 São João del Rei, MG, Brazil.
authors.forename: R C
authors.initials: RC
authors.lastname: Chaves
authors.affiliation: Department of Bioscience - Freshwater Ecology, Aarhus University, Vejlsøvej 25, 8600 Silkeborg, Denmark.
authors.forename: D
authors.initials: D
authors.lastname: Graeber
authors.affiliation: Department of Biosystems Engineering, Federal University of São João del-Rei, Praça Dom Helvécio 74, 36301-160 São João del Rei, MG, Brazil.
authors.forename: B
authors.initials: B
authors.lastname: Gücker
mesh_terms: D000383:Agriculture; D004784:Environmental Monitoring; D005227:Fatty Acids / Q000032:analysis*; D006812:Humic Substances / Q000032:analysis; D045483:Rivers / Q000737:chemistry*; D014329:Tropical Climate; D014507:Urbanization; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D005227:Fatty Acids; D006812:Humic Substances; D014874:Water Pollutants, Chemical
keywords: Fatty acid biomarkers; River monitoring; Suspended particulate organic matter; Tropical rivers; Urbanization