Global effects of agriculture on fluvial dissolved organic matter

Abstract

Agricultural land covers approximately 40% of Earth’s land surface and affects hydromorphological, biogeochemical and ecological characteristics of fluvial networks. In the northern temperate region, agriculture also strongly affects the amount and molecular composition of dissolved organic matter (DOM), which constitutes the main vector of carbon transport from soils to fluvial networks and to the sea, and is involved in a large variety of biogeochemical processes. Here, we provide first evidence about the wider occurrence of agricultural impacts on the concentration and composition of fluvial DOM across climate zones of the northern and southern hemispheres. Both extensive and intensive farming altered fluvial DOM towards a more microbial and less plant-derived composition. Moreover, intensive farming significantly increased dissolved organic nitrogen (DON) concentrations. The DOM composition change and DON concentration increase differed among climate zones and could be related to the intensity of current and historical nitrogen fertilizer use. As a result of agriculture intensification, increased DON concentrations and a more microbial-like DOM composition likely will enhance the reactivity of catchment DOM emissions, thereby fuelling the biogeochemical processing in fluvial networks, and resulting in higher ecosystem productivity and CO2 outgassing.

Identifying the Molecular Signatures of Agricultural Expansion in Amazonian Headwater Streams

“…Therefore, studies are urgently needed to better understand how anthropogenic activities impact the amount and composition of dissolved OM (DOM) mobilized from terrestrial ecosystems into aquatic networks. Previous studies have shown that mobilization of aged dissolved organic carbon (DOC) is positively correlated with human disturbance worldwide (Butman et al, ) and that anthropogenic pressures such as land cover change impact DOM composition (Graeber et al, ; Heinz et al, ; Wilson & Xenopoulos, ). This is fundamentally important as DOM composition controls its photoreactivity, bioavailability, and ultimately its persistence in the environment (D'Andrilli et al, ; Kellerman et al, ; Lu et al, ; Maizel et al, ; Marschner & Kalbitz, ; Spencer et al, ).…”

Effects of agricultural land use on fluvial carbon dioxide, methane and nitrous oxide concentrations in a large European river, the Meuse (Belgium)

“…Increased water residence time and water transparency due to impoundments can lead to low CO 2 levels related to enhanced primary production . Agriculture can enhance mobilisation of labile soil organic matter (Wilson and Xenopoulos, 2009;Graeber et al, 2012Graeber et al, , 2015Lambert et al, 2017) and potentially enhance organic matter degradation and the production of CO 2 and CH 4 in rivers, although this has been seldom investigated (Bodmer et al, 2016). Leaching of nitrogen from artificial fertilizers from agricultural soils leads to enhanced in-stream N 2 O production, presumably related to enhanced denitrification (Beaulieu et al, 2011).…”

Variação Sazonal Do Carbono Orgânico Dissolvido (Cod) E Propriedades Ópticas Da Matéria Orgânica Em Diferentes Sistemas De Pastagem E De Soja No Estado De Mato Grosso

“…A further intensification of agriculture in tropical developing countries is expected since, in addition to population growth, food demand per capita will increase with the increase in gross domestic product in the future (Graeber et al, 2015). Thus, intensification of agriculture may result in the release of large quantities of biogeochemically reactive DOM to river networks, altering the DOM-related biogeochemical cycles, and increasing the productivity, respiration, and depletion of CO 2 from river networks (Graeber et al, 2015).…”

“…The biogeochemical characterization of the dissolved organic matter (DOM) based on fluorescence allows the detection of differences between natural and anthropogenic DOM sources in rivers impacted by agricultural residues ; (Wilson e Xenopoulos, 2008). A combination of optical properties (fluorescence and absorption), coupled with conventional DOC measurements, can be used to understand how changes and intensification in agricultural land use can modify the quantity and composition of DOM (Graeber et al, 2015).…”