References of "Borges, Alberto"
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See detailVertical Distribution of Functional Potential and Active Microbial Communities in Meromictic Lake Kivu
İnceoğlu, Özgul; Llirós, Marc; Crowe, Sean A. et al

in Microbial Ecology (2015)

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See detailApplications of stable isotopes in environmental studies at the University of Liege
Sturaro, Nicolas ULg; Borges, Alberto ULg; Das, Krishna ULg et al

Poster (2015, March 26)

Measurement and use of stable isotope ratios have a long history at the University of Liege (Belgium). Since at least 30 years, applications of stable isotopes in marine ecosystems have been developed ... [more ▼]

Measurement and use of stable isotope ratios have a long history at the University of Liege (Belgium). Since at least 30 years, applications of stable isotopes in marine ecosystems have been developed within the Laboratory of Oceanology and, more recently, within the Chemical Oceanography Unit. In the Laboratory of Oceanology, one research axis is the measurement of stable isotope composition (C, N, S) in organic matter to delineate trophic web structure and to study animal diet, their trophic niches and their alteration by human activities. This methodology has been successively applied worldwide in different habitats and ecosystems (marine, freshwater, terrestrial) in temperate and tropical areas. Mediterranean food web and fish trophic ecology have received a particular attention. Coupling between trophic ecology and ecotoxicology is another area of investigation. This has been applied mainly to marine vertebrates and freshwater ecosystems. Stable isotope labelling is also used in our laboratory to study and quantify various ecological processes such as inorganic nitrogen incorporation and trophic transfers. The laboratory facilities, renewed in 2012 and managed by Dr. Gilles Lepoint, are composed of an elemental analyser (EA, vario MICRO cube, Elementar) and a gas chromatography (GC, Agilent) coupled to an isotope ratio mass spectrometer (IRMS, Isoprime 100). The GC is also equipped with a quadrupole mass spectrometer. In 2014, the Chemical Oceanography Unit, headed by Dr. Alberto Borges, has acquired and implemented an off-axis cavity ring-down spectroscopy (CRDS) for the measurements of δ15Nα, δ15Nβ, δ18O of N2O. This enables characterization of the N2O origin in a variety of aquatic environments including groundwater in Wallonia, rivers and lakes in Wallonia and Africa, coastal environments (Scheldt estuary, Lake Grevelingen, North Sea), Mediterranean seagrass beds, and Antarctic and Arctic sea-ice. [less ▲]

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See detailInorhanic and organic carbon spatial variability in the Congo River during high waters (December 2013) and low waters (June 2014)
Borges, Alberto ULg; Bouillon, S; Teodoru, C et al

Conference (2015, February 23)

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See detailCyanobacteria - the constructors of travertines?
Kleinteich, Julia; Stelmach Pessi, Igor ULg; Velazquez, David et al

Conference (2015, February)

Cyanobacteria are participating in carbonate build-up and travertine formation in the Belgian river Hoyoux and its tributaries. In this study, we sampled calcareous material from travertines and oncoliths ... [more ▼]

Cyanobacteria are participating in carbonate build-up and travertine formation in the Belgian river Hoyoux and its tributaries. In this study, we sampled calcareous material from travertines and oncoliths from four sampling sites on the Hoyoux river and Triffoy brook. In addition, the water chemistry was determined. The structure of the material was analyzed by Scanning Electron Microscopy and Raman microscopy (?°. The dominant cyanobacterial species was isolated and identified on the basis of microscopic observation and amplification of the 16S-ITS fragment as Phormidium sp., likely functioning as the ‘architect’ of the travertine system. In order to describe the full diversity of the travertine system and to discriminate between the active fraction and inactive or dead organic matter, DNA as well as RNA was extracted from the travertine material, amplified using cyanobacteria specific primers and sequenced by 454 pyrosequencing. To detect seasonal changes in the biological activity, summer and winter time points were compared. This study reveals the ecology of an overlooked environment in Belgian river systems and tries to explain the build-up of travertines. [less ▲]

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See detailThe variability of primary production in the ocean: from the synoptic to the global scale: The 45th International Liege Colloquium on Ocean Dynamics, Liege, Belgium, May 13-17, 2013
Grégoire, Marilaure ULg; Levy, Marina; Marra, John et al

Book published by Journal of Marine System, Elsevier Science (2015)

The 45th International Liege Colloquium on Ocean Dynamics (http://modb.oce.ulg.ac.be/colloquium/) gathered two hundreds scientists from around the world to discuss new insights related to the evaluation ... [more ▼]

The 45th International Liege Colloquium on Ocean Dynamics (http://modb.oce.ulg.ac.be/colloquium/) gathered two hundreds scientists from around the world to discuss new insights related to the evaluation of primary production at various spatial and temporal scales and in different regions of the world ocean (e.g. the polar and sea-ice region, the coastal and the deep ocean). Over the past two decades, substantial efforts were deployed to evaluate oceanic primary production. These efforts include in situ measurements of uptake rates using isotopic techniques, remote sensing, autonomous instrumentation for bio-optics, carbon or oxygen measurements, and the development of semi-empirical to complex biogeochemical models. The colloquium presented the opportunity to review the current knowledge in the estimation of primary production, and to assess the impact of physical processes on ocean productivity. Particular attention focused on the importance of physical processes at different spatial and temporal scales for controlling the level and variability of primary production and on the development of adequate methodologies to tackle this variability in order to derive large-scale, climate-driven budgets. Refined biogeochemical models considering for instance phytoplankton physiology, the representation of variable elemental stoichiometric ratios, the role of mixotrophy as well as satellite algorithms that are now able to simulate the plankton functional types are good candidates for scaling up. Contributions dealing with the difficult issue of interoperability of in-situ, satellite and modelling estimates of primary production were presented. Details on the terms of reference as well as the thematic session that were organized can be found at http://modb.oce.ulg.ac.be/?page=colloquium&year=2013. [less ▲]

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See detailMethanotrophy within the water column of a large meromictic tropical lake (Lake Kivu, East Africa)
Morana, C.; Borges, Alberto ULg; Roland, Fleur ULg et al

in Biogeosciences (2015), 12(7), 2077-2088

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See detailDynamics of greenhouse gases (CO2, CH4, N2O) along the Zambezi River and major tributaries, and their importance in the riverine carbon budget
Teodoru, C. R.; Nyoni, F. C.; Borges, Alberto ULg et al

in Biogeosciences (2015), 12(8), 2431-2453

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See detailAcoustic monitoring of O2 production of a seagrass meadow
Felisberto, Paulo; Jesus, Sérgio M.; Zabel, Friedrich et al

in Journal of Experimental Marine Biology and Ecology (2015), 464(0), 75-87

Acoustic data were acquired in October 2011 over a Posidonia oceanica meadow in the Bay of la Revellata, Calvi, Corsica. The purpose was to develop an acoustic system for monitoring the oxygen (O2 ... [more ▼]

Acoustic data were acquired in October 2011 over a Posidonia oceanica meadow in the Bay of la Revellata, Calvi, Corsica. The purpose was to develop an acoustic system for monitoring the oxygen (O2) production of an entire seagrass meadow. In a shallow water area (b38 m), densely covered by P. oceanica, a sound source transmitted signals in 3 different bands (400–800 Hz, 1.5–3.5 kHz and 6.5–8.5 kHz) toward three self-recording hydrophones at a distance of 100 m, over the period of oneweek. The data showa high correlation between the diel cycle of the acoustic signals' energy received by the hydrophones and the temporal changes in water column O2 concentration as measured by optodes. The results thus show that a simple acoustic acquisition system can be used to monitor the O2-based productivity of a seagrass meadow at the ecosystem level with high temporal resolution. The finding of a significant production of O2 as bubbles in seagrass ecosystems suggests that net primary production is underestimated by methods that rely on the mass balance of dissolved O2 measurements. [less ▲]

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See detailThe age of river-transported carbon: A global perspective
Marwick, Trent R.; Tamooh, Fredrick; Teodoru, Cristian R. et al

in Global Biogeochemical Cycles (2015), 29(2), 122--137

The role played by river networks in regional and global carbon (C) budgets is receiving increasing attention. Despite the potential of radiocarbon measurements (Δ14C) to elucidate sources and cycling of ... [more ▼]

The role played by river networks in regional and global carbon (C) budgets is receiving increasing attention. Despite the potential of radiocarbon measurements (Δ14C) to elucidate sources and cycling of different riverine C pools, there remain large regions for which no data are available and no comprehensive attempts to synthesize the available information and examine global patterns in the 14C content of different riverine C pools. Here we present new 14C data on particulate and dissolved organic C (POC and DOC) from six river basins in tropical and subtropical Africa and compiled >1400 literature Δ14C data and ancillary parameters from rivers globally. Our analysis reveals a consistent pattern whereby POC is progressively older in systems carrying higher sediment loads, coinciding with a lower organic carbon content. At the global scale, this pattern leads to a proposed global median Δ14C signature of −203‰, corresponding to an age of ~1800 years B.P. For DOC exported to the coastal zone, we predict a modern (decadal) age (Δ14C = +22 to +46‰), and paired data sets confirm that riverine DOC is generally more recent in origin than POC—in contrast to the situation in ocean environments. Weathering regimes complicate the interpretation of 14C ages of dissolved inorganic carbon, but the available data favor the hypothesis that in most cases, more recent organic C is preferentially mineralized. [less ▲]

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See detailBiogeochemical processes and buffering capacity concurrently affect acidification in a seasonally hypoxic coastal marine basin
Hagens, M.; Slomp, C. P.; Meysman, F. J. R. et al

in Biogeosciences (2015), 12(5), 1561--1583

Coastal areas are impacted by multiple natural and anthropogenic processes and experience stronger pH fluctuations than the open ocean. These variations can weaken or intensify the ocean acidification ... [more ▼]

Coastal areas are impacted by multiple natural and anthropogenic processes and experience stronger pH fluctuations than the open ocean. These variations can weaken or intensify the ocean acidification signal induced by increasing atmospheric pCO2. The development of eutrophication-induced hypoxia intensifies coastal acidification, since the CO2 produced during respiration decreases the buffering capacity in any hypoxic bottom water. To assess the combined ecosystem impacts of acidification and hypoxia, we quantified the seasonal variation in pH and oxygen dynamics in the water column of a seasonally stratified coastal basin (Lake Grevelingen, the Netherlands). Monthly water-column chemistry measurements were complemented with estimates of primary production and respiration using O2 light–dark incubations, in addition to sediment–water fluxes of dissolved inorganic carbon (DIC) and total alkalinity (TA). The resulting data set was used to set up a proton budget on a seasonal scale. Temperature-induced seasonal stratification combined with a high community respiration was responsible for the depletion of oxygen in the bottom water in summer. The surface water showed strong seasonal variation in process rates (primary production, CO2 air–sea exchange), but relatively small seasonal pH fluctuations (0.46 units on the total hydrogen ion scale). In contrast, the bottom water showed less seasonality in biogeochemical rates (respiration, sediment–water exchange), but stronger pH fluctuations (0.60 units). This marked difference in pH dynamics could be attributed to a substantial reduction in the acid–base buffering capacity of the hypoxic bottom water in the summer period. Our results highlight the importance of acid–base buffering in the pH dynamics of coastal systems and illustrate the increasing vulnerability of hypoxic, CO2-rich waters to any acidifying process. [less ▲]

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See detailTechnical Note: Large overestimation of pCO2 calculated from pH and alkalinity in acidic, organic-rich freshwaters
Abril, G; Bouillon, S; Darchambeau, François ULg et al

in Biogeosciences (2015), 12(1), 67-78

Inland waters have been recognized as a significant source of carbon dioxide (CO2) to the atmosphere at the global scale. Fluxes of CO2 between aquatic systems and the atmosphere are calculated from the ... [more ▼]

Inland waters have been recognized as a significant source of carbon dioxide (CO2) to the atmosphere at the global scale. Fluxes of CO2 between aquatic systems and the atmosphere are calculated from the gas transfer velocity and the water–air gradient of the partial pressure of CO2 (pCO2). Currently, direct measurements of water pCO2 remain scarce in freshwaters, and most published pCO2 data are calculated from temperature, pH and total alkalinity (TA). Here, we compare calculated (pH and TA) and measured (equilibrator and headspace) water pCO2 in a large array of temperate and tropical freshwaters. The 761 data points cover a wide range of values for TA (0 to 14 200 μmol L􀀀1), pH (3.94 to 9.17), measured pCO2 (36 to 23 000 ppmv), and dissolved organic carbon (DOC) (29 to 3970 μmol L􀀀1). Calculated pCO2 were >10% higher than measured pCO2 in 60% of the samples (with a median overestimation of calculated pCO2 compared to measured pCO2 of 2560 ppmv) and were >100% higher in the 25% most organic-rich and acidic samples (with a median overestimation of 9080 ppmv). We suggest these large overestimations of calculated pCO2 with respect to measured pCO2 are due to the combination of two cumulative effects: (1) a more significant contribution of organic acids anions to TA in waters with low carbonate alkalinity and high DOC concentrations; (2) a lower buffering capacity of the carbonate system at low pH, which increases the sensitivity of calculated pCO2 to TA in acidic and organicrich waters. No empirical relationship could be derived from our data set in order to correct calculated pCO2 for this bias. Owing to the widespread distribution of acidic, organic-rich freshwaters, we conclude that regional and global estimates of CO2 outgassing from freshwaters based on pH and TA data only are most likely overestimated, although the magnitude of the overestimation needs further quantitative analysis. Direct measurements of pCO2 are recommended in inland waters in general, and in particular in acidic, poorly buffered freshwaters [less ▲]

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See detailAnaerobic methane oxidation in two tropical freshwater systems
Roland, Fleur ULg; Darchambeau, François ULg; Crowe, SA et al

Poster (2014, May 05)

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See detailAmmonia Oxidising Archaea in the OMZ of a freshwater African Lake
Lliros, M; Ingeoglu, O; Garcia-Armisen, T et al

Poster (2014, May 05)

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See detailRates of microbial sulfur oxidation in low oxygen environments
Crowe, SA; Canfield, DE; Sturm, A et al

Poster (2014, May 05)

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