ORCID Profile
0000-0003-0731-8655
Current Organisation
CNRS
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Publisher: Elsevier BV
Date: 05-2012
Publisher: Elsevier BV
Date: 09-2016
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5EM00462D
Abstract: Dissolved organic matter (DOM) was characterised in water s les s led in the Lower Kinabatangan River Catchment, Sabah, Malaysia between October 2009 and May 2010.
Publisher: Copernicus GmbH
Date: 05-11-2012
Abstract: Abstract. Floodplain restoration changes the nitrate delivery pattern and dissolved organic matter pool in backwaters, though the effects these changes have are not yet well known. We performed two mesocosm experiments on floodplain sediments to quantify the nitrate metabolism in two types of floodplains. Rates of denitrification, dissimilatory nitrate reduction to ammonium (DNRA) and anammox were measured using 15N-NO3 tracer additions in mesocosms of undisturbed floodplain sediments originating from (1) restored and (2) disconnected sites in the Alluvial Zone National Park on the Danube River downstream of Vienna, Austria. DNRA rates were an order of magnitude lower than denitrification and neither rate was affected by changes in nitrate delivery pattern or organic matter quality. Anammox was not detected at any of the sites. Denitrification was out-competed by assimilation, which was estimated to use up to 70% of the available nitrate. Overall, denitrification was higher in the restored sites, with mean rates of 5.7 ± 2.8 mmol N m−2 h−1 compared to the disconnected site (0.6 ± 0.5 mmol N m−2 h−1). In addition, ratios of N2O : N2 were lower in the restored site indicating a more complete denitrification. Nitrate addition had neither an effect on denitrification, nor on the N2O : N2 ratio. However, DOM (dissolved organic matter) quality significantly changed the N2O : N2 ratio in both sites. Addition of riverine-derived organic matter lowered the N2O : N2 ratio in the disconnected site, whereas addition of floodplain-derived organic matter increased the N2O : N2 ratio in the restored site. These results demonstrate that increasing floodplains hydrological connection to the main river channel increases nitrogen retention and decreases nitrous oxide emissions.
Publisher: American Geophysical Union (AGU)
Date: 2021
DOI: 10.1029/2020GB006719
Abstract: Permafrost degradation is delivering bioavailable dissolved organic matter (DOM) and inorganic nutrients to surface water networks. While these permafrost subsidies represent a small portion of total fluvial DOM and nutrient fluxes, they could influence food webs and net ecosystem carbon balance via priming or nutrient effects that destabilize background DOM. We investigated how addition of biolabile carbon (acetate) and inorganic nutrients (nitrogen and phosphorus) affected DOM decomposition with 28‐day incubations. We incubated late‐summer stream water from 23 locations nested in seven northern or high‐altitude regions in Asia, Europe, and North America. DOM loss ranged from 3% to 52%, showing a variety of longitudinal patterns within stream networks. DOM optical properties varied widely, but DOM showed compositional similarity based on Fourier transform ion cyclotron resonance mass spectrometry (FT‐ICR MS) analysis. Addition of acetate and nutrients decreased bulk DOM mineralization (i.e., negative priming), with more negative effects on biodegradable DOM but neutral or positive effects on stable DOM. Unexpectedly, acetate and nutrients triggered breakdown of colored DOM (CDOM), with median decreases of 1.6% in the control and 22% in the amended treatment. Additionally, the uptake of added acetate was strongly limited by nutrient availability across sites. These findings suggest that biolabile DOM and nutrients released from degrading permafrost may decrease background DOM mineralization but alter stoichiometry and light conditions in receiving waterbodies. We conclude that priming and nutrient effects are coupled in northern aquatic ecosystems and that quantifying two‐way interactions between DOM properties and environmental conditions could resolve conflicting observations about the drivers of DOM in permafrost zone waterways.
Publisher: Elsevier BV
Date: 09-2011
Publisher: IWA Publishing
Date: 19-04-2014
DOI: 10.2166/NH.2014.196
Abstract: Spatial patterns and trends in the concentration and quality of dissolved organic matter (DOM) are characterised across a tropical agricultural catchment using ultraviolet (UV)-visible absorbance, and fluorescence spectroscopy. Related determination of the environmental isotopes 18O and 2H clarify the dynamics of catchment water movement. Water s les were collected from the Kinabatangan River, Borneo, and selected tributaries in August and September 2008 in four regions with oil palm plantations (KB1, KB2, KB3 and KB4). The isotopic compositions of surface waters suggest that canals were characterised by a strong evaporative effect than tributaries and streams with more natural, forested vegetation. DOM was characterised by variations in UV absorbance and spectral slope. In idual fluorescence excitation–emission matrices were decomposed by Parallel Factor Analysis (PARAFAC) and three components extracted (C1, C2 and C3). Components C2 and C3 both appear to be derived from microbial sources and/or photo-degradation. The PARAFAC components indicate a clear trend of increasing DOM degradation as waters pass through the catchment. It is hypothesised that upstream DOM is rapidly photo and microbially degraded to less fluorescent DOM, while DOM concentration and character of DOM downstream is controlled by the hydrology, specifically by variations in the rate of water movement.
No related grants have been discovered for Gilles Pinay.