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Borges AV, Deirmendjian L, Bouillon S, Okello W, Lambert T, Roland FAE, Razanamahandry VF, Voarintsoa NRG, Darchambeau F, Kimirei IA, Descy JP, Allen GH, Morana C. Greenhouse gas emissions from African lakes are no longer a blind spot. Sci Adv 2022; 8:eabi8716. [PMID: 35749499 PMCID: PMC9232103 DOI: 10.1126/sciadv.abi8716] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 05/09/2022] [Indexed: 06/15/2023]
Abstract
Natural lakes are thought to be globally important sources of greenhouse gases (CO2, CH4, and N2O) to the atmosphere although nearly no data have been previously reported from Africa. We collected CO2, CH4, and N2O data in 24 African lakes that accounted for 49% of total lacustrine surface area of the African continent and covered a wide range of morphology and productivity. The surface water concentrations of dissolved CO2 were much lower than values attributed in current literature to tropical lakes and lower than in boreal systems because of a higher productivity. In contrast, surface water-dissolved CH4 concentrations were generally higher than in boreal systems. The lowest CO2 and the highest CH4 concentrations were observed in the more shallow and productive lakes. Emissions of CO2 may likely have been substantially overestimated by a factor between 9 and 18 in African lakes and between 6 and 26 in pan-tropical lakes.
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Affiliation(s)
| | | | - Steven Bouillon
- Department of Earth and Environmental Sciences, KU Leuven, Leuven, Belgium
| | - William Okello
- Department of Limnology, National Fisheries Resource Research Institute, Jinja, Uganda
| | | | | | | | | | | | | | | | - George H. Allen
- Department of Geography, Texas A&M University, College Station, TX, USA
| | - Cédric Morana
- Chemical Oceanography Unit, University of Liège, Liège, Belgium
- Department of Earth and Environmental Sciences, KU Leuven, Leuven, Belgium
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Uzunov B, Stefanova K, Radkova M, Descy JP, Gärtner G, Stoyneva-Gärtner M. First Report on Microcystis as a Potential Microviridin Producer in Bulgarian Waterbodies. Toxins (Basel) 2021; 13:toxins13070448. [PMID: 34203459 PMCID: PMC8310014 DOI: 10.3390/toxins13070448] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2021] [Revised: 06/24/2021] [Accepted: 06/25/2021] [Indexed: 12/30/2022] Open
Abstract
Bulgaria, situated on the Balkan Peninsula, is rich in small and shallow, natural and man-made non-lotic waterbodies, which are threatened by blooms of Cyanoprokaryota/Cyanobacteria. Although cyanotoxins in Bulgarian surface waters are receiving increased attention, there is no information on microviridins and their producers. This paper presents results from a phytoplankton study, conducted in August 2019 in three lakes (Durankulak, Vaya, Uzungeren) and five reservoirs (Duvanli, Mandra, Poroy, Sinyata Reka, Zhrebchevo) in which a molecular-genetic analysis (PCR based on the precursor mdnA gene and subsequent translation to amino acid alignments), combined with conventional light microscopy and an HPLC analysis of marker pigments, were applied for the identification of potential microviridin producers. The results provide evidence that ten strains of the genus Microcystis, and of its most widespread species M. aeruginosa in particular, are potentially toxigenic in respect to microviridins. The mdnA sequences were obtained from all studied waterbodies and their translation to amino-acid alignments revealed the presence of five microviridin variants (types B/C, Izancya, CBJ55500.1 (Microcystis 199), and MC19, as well as a variant, which was very close to type A). This study adds to the general understanding of the microviridin occurrence, producers, and sequence diversity.
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Affiliation(s)
- Blagoy Uzunov
- Department of Botany, Faculty of Biology, Sofia University, 8 blvd. Dragan Zankov, 1164 Sofia, Bulgaria
- Correspondence: (B.U.); (M.S.-G.)
| | - Katerina Stefanova
- AgroBioInstitute, Bulgarian Agricultural Academy, 8 blvd. Dragan Zankov, 1164 Sofia, Bulgaria; (K.S.); (M.R.)
| | - Mariana Radkova
- AgroBioInstitute, Bulgarian Agricultural Academy, 8 blvd. Dragan Zankov, 1164 Sofia, Bulgaria; (K.S.); (M.R.)
| | - Jean-Pierre Descy
- Unité d’Océanographie Chimique, Université de Liège, Sart Tilman, 4000 Liège, Belgium;
| | - Georg Gärtner
- Institut für Botanik der Universität Innsbruck, Sternwartestrasse 15, 6020 Innsbruck, Austria;
| | - Maya Stoyneva-Gärtner
- Department of Botany, Faculty of Biology, Sofia University, 8 blvd. Dragan Zankov, 1164 Sofia, Bulgaria
- Correspondence: (B.U.); (M.S.-G.)
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Minaudo C, Abonyi A, Leitão M, Lançon AM, Floury M, Descy JP, Moatar F. Long-term impacts of nutrient control, climate change, and invasive clams on phytoplankton and cyanobacteria biomass in a large temperate river. Sci Total Environ 2021; 756:144074. [PMID: 33303198 DOI: 10.1016/j.scitotenv.2020.144074] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 11/17/2020] [Accepted: 11/20/2020] [Indexed: 06/12/2023]
Abstract
Recent studies suggest that climate change, with warmer water temperatures and lower and longer low flows, may enhance harmful planktic cyanobacterial growth in lakes and large rivers. Concomitantly, controlling nutrient loadings has proven effective in reducing phytoplankton biomass especially in North America and Western Europe. In addition, the impact of invasive benthic filter-feeder species such as Corbicula on phytoplankton has largely been overlooked in large rivers, leading to even more uncertainty in predicting future trajectories in river water quality. To investigate how nutrient control, climate change and invasion of benthic filter-feeders may affect phytoplankton biomass and composition, we assembled a large database on the entire water course of the River Loire (France) over three decades (1991-2019). We focus on cyanobacteria to provide an in-depth analysis of the 30-year trend and insights on future possible trajectories. Since 1991, total phytoplankton and cyanobacteria biomasses have decreased 10-fold despite warmer water temperature (+0.23 °C·decade-1) and lower summer flow (-0.25 L·s-1·km-2·decade-1). In the long-term, the contribution of planktic cyanobacteria to total biomass was on average 2.8%. The main factors driving total phytoplankton and cyanobacteria biomasses were total phosphorus (4-fold decrease), the abundance of Corbicula clams (from absence before 1998 to 250-1250 individuals·m-2 after 2010), the duration of summer low flows and the intensity of summer heatwaves. The River Loire constitutes an example in Europe of how nutrient control can be an efficient mitigation strategy, counteracting already visible effects of climate change on the thermal regime and flow pattern of the river. This may hold true under future conditions, but further work is needed to account for the climate trajectory, land and water use scenarios, the risk of enhanced benthic biofilm and macrophyte proliferation, together with the spread of invasive filter-feeding bivalves.
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Affiliation(s)
- Camille Minaudo
- Physics of Aquatic Systems Laboratory, Margaretha Kamprad Chair, EPFL-APHYS, Lausanne, Switzerland.
| | - András Abonyi
- WasserCluster Lunz Biologische Station GmbH, Lunz am See, Austria; Centre for Ecological Research, Danube Research Institute, Budapest, Hungary
| | | | | | - Mathieu Floury
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, ENTPE, UMR 5023 LEHNA, F-69622, Villeurbanne, France; INRAE, UR RiverLy, Lyon-Villeurbanne, France
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Roland FAE, Borges AV, Darchambeau F, Llirós M, Descy JP, Morana C. The possible occurrence of iron-dependent anaerobic methane oxidation in an Archean Ocean analogue. Sci Rep 2021; 11:1597. [PMID: 33452366 PMCID: PMC7810693 DOI: 10.1038/s41598-021-81210-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Accepted: 01/05/2021] [Indexed: 11/24/2022] Open
Abstract
In the ferruginous and anoxic early Earth oceans, photoferrotrophy drove most of the biological production before the advent of oxygenic photosynthesis, but its association with ferric iron (Fe3+) dependent anaerobic methane (CH4) oxidation (AOM) has been poorly investigated. We studied AOM in Kabuno Bay, a modern analogue to the Archean Ocean (anoxic bottom waters and dissolved Fe concentrations > 600 µmol L-1). Aerobic and anaerobic CH4 oxidation rates up to 0.12 ± 0.03 and 51 ± 1 µmol L-1 d-1, respectively, were put in evidence. In the Fe oxidation-reduction zone, we observed high concentration of Bacteriochlorophyll e (biomarker of the anoxygenic photoautotrophs), which co-occurred with the maximum CH4 oxidation peaks, and a high abundance of Candidatus Methanoperedens, which can couple AOM to Fe3+ reduction. In addition, comparison of measured CH4 oxidation rates with electron acceptor fluxes suggest that AOM could mainly rely on Fe3+ produced by photoferrotrophs. Further experiments specifically targeted to investigate the interactions between photoferrotrophs and AOM would be of considerable interest. Indeed, ferric Fe3+-driven AOM has been poorly envisaged as a possible metabolic process in the Archean ocean, but this can potentially change the conceptualization and modelling of metabolic and geochemical processes controlling climate conditions in the Early Earth.
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Affiliation(s)
- Fleur A E Roland
- Chemical Oceanography Unit, Université de Liège, Liège, Belgium.
| | | | | | - Marc Llirós
- Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Barcelona, Spain
- Girona Biomedical Research Institute, Salt, Catalunya, Spain
| | | | - Cédric Morana
- Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven (KU Leuven), Leuven, Belgium
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Latli A, Descy JP, Mondy CP, Floury M, Viroux L, Otjacques W, Marescaux J, Depiereux E, Ovidio M, Usseglio-Polatera P, Kestemont P. Long-term trends in trait structure of riverine communities facing predation risk increase and trophic resource decline. Ecol Appl 2017; 27:2458-2474. [PMID: 28873278 DOI: 10.1002/eap.1621] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Revised: 06/26/2017] [Accepted: 07/20/2017] [Indexed: 06/07/2023]
Abstract
Many large European rivers have undergone multiple pressures that have strongly impaired ecosystem functioning at different spatial and temporal scales. Global warming and other environmental changes have favored the success of invasive species, deeply modifying the structure of aquatic communities in large rivers. Some exogenous species could alter trophic interactions within assemblages by increasing the predation risk for potential prey species (top-down effect) and limiting the dynamics of others via resource availability limitation (bottom-up effect). Furthermore, large transboundary rivers are complex aquatic ecosystems that have often been poorly investigated so that data for assessing long-term ecological trends are missing. In this study, we propose an original approach for investigating long-term combined effects of global warming, trophic resource decrease, predation risk, and water quality variations on the trait-based structure of macroinvertebrate and fish assemblages over 26 yr (1985-2011) and 427-km stretch of the river Meuse (France and Belgium). The study of temporal variations in biological, physiological, and ecological traits of macroinvertebrate and fish allowed identifying community trends and distinguishing impacts of environmental perturbations from those induced by biological alterations. We provide evidence, for this large European river, of an increase in water temperature (close to 1°C) and a decrease in phytoplankton biomass (-85%), as well as independent effects of these changes on both invertebrate and fish communities. The reduction of trophic resources in the water column by invasive molluscs has dramatically affected the density of omnivorous fish in favor of invertebrate feeders, while scrapers became the major feeding guild among invertebrates. Macroinvertebrate and fish communities have shifted from large-sized organisms with low fecundity to prolific, small-sized organisms, with early maturity, as a response to increased predation pressure.
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Affiliation(s)
- Adrien Latli
- Research Unit in Environmental and Evolutionary Ecology, University of Namur, rue de Bruxelles 61, B-5000, Namur, Belgium
| | - Jean-Pierre Descy
- Research Unit in Environmental and Evolutionary Ecology, University of Namur, rue de Bruxelles 61, B-5000, Namur, Belgium
| | - Cédric P Mondy
- Biodiversity and Plasticity in Hydrosystems, CNRS UMR 5023 LEHNA, University Lyon 1, Bât Forel, 69622, Villeurbanne Cedex, France
| | - Mathieu Floury
- Aquatic Environments, Ecology and Pollution, UR MALY, Irstea, 5 rue de la Doua, 70077, 69626, Villeurbanne, France
| | - Laurent Viroux
- Research Unit in Environmental and Evolutionary Ecology, University of Namur, rue de Bruxelles 61, B-5000, Namur, Belgium
| | - William Otjacques
- Research Unit in Environmental and Evolutionary Ecology, University of Namur, rue de Bruxelles 61, B-5000, Namur, Belgium
| | - Jonathan Marescaux
- Research Unit in Environmental and Evolutionary Ecology, University of Namur, rue de Bruxelles 61, B-5000, Namur, Belgium
| | - Eric Depiereux
- Research Unit in Environmental and Evolutionary Ecology, University of Namur, rue de Bruxelles 61, B-5000, Namur, Belgium
| | - Michael Ovidio
- Laboratory of Fish Demography and Hydroecology, University of Liège, Belgium
| | - Philippe Usseglio-Polatera
- Interdisciplinary Laboratory for Continental Environments, CNRS UMR 7360 LIEC, University of Lorraine, Campus Bridoux, 57070, Metz, France
| | - Patrick Kestemont
- Research Unit in Environmental and Evolutionary Ecology, University of Namur, rue de Bruxelles 61, B-5000, Namur, Belgium
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Sarmento H, Isumbisho M, Stenuite S, Darchambeau F, Leporcq B, Descy JP. Phytoplankton ecology of Lake Kivu (eastern Africa): biomass, production and elemental ratios. ACTA ACUST UNITED AC 2017. [DOI: 10.1080/03680770.2009.11902221] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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İnceoğlu Ö, Llirós M, Crowe SA, García-Armisen T, Morana C, Darchambeau F, Borges AV, Descy JP, Servais P. Vertical Distribution of Functional Potential and Active Microbial Communities in Meromictic Lake Kivu. Microb Ecol 2015; 70:596-611. [PMID: 25912922 DOI: 10.1007/s00248-015-0612-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 04/02/2015] [Indexed: 06/04/2023]
Abstract
The microbial community composition in meromictic Lake Kivu, with one of the largest CH4 reservoirs, was studied using 16S rDNA and ribosomal RNA (rRNA) pyrosequencing during the dry and rainy seasons. Highly abundant taxa were shared in a high percentage between bulk (DNA-based) and active (RNA-based) bacterial communities, whereas a high proportion of rare species was detected only in either an active or bulk community, indicating the existence of a potentially active rare biosphere and the possible underestimation of diversity detected when using only one nucleic acid pool. Most taxa identified as generalists were abundant, and those identified as specialists were more likely to be rare in the bulk community. The overall number of environmental parameters that could explain the variation was higher for abundant taxa in comparison to rare taxa. Clustering analysis based on operational taxonomic units (OTUs at 0.03 cutoff) level revealed significant and systematic microbial community composition shifts with depth. In the oxic zone, Actinobacteria were found highly dominant in the bulk community but not in the metabolically active community. In the oxic-anoxic transition zone, highly abundant potentially active Nitrospira and Methylococcales were observed. The co-occurrence of potentially active sulfur-oxidizing and sulfate-reducing bacteria in the anoxic zone may suggest the presence of an active yet cryptic sulfur cycle.
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Affiliation(s)
- Özgul İnceoğlu
- Ecologie des Systèmes Aquatiques, Université Libre de Bruxelles, Brussel, Belgium.
| | - Marc Llirós
- Laboratory of Freshwater Ecology, Université de Namur, Namur, Belgium
- Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Sean A Crowe
- Departments of Microbiology and Immunology, and Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, Canada
| | | | - Cedric Morana
- Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven, Leuven, Belgium
| | | | | | - Jean-Pierre Descy
- Laboratory of Freshwater Ecology, Université de Namur, Namur, Belgium
| | - Pierre Servais
- Ecologie des Systèmes Aquatiques, Université Libre de Bruxelles, Brussel, Belgium
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Stoyneva M, Traykov I, Tosheva A, Uzunov B, Zidarova R, Descy JP. Comparison of ecological state/potential assessment of 19 Bulgarian water bodies based on macrophytes and phytoplankton (2011–2012). BIOTECHNOL BIOTEC EQ 2015. [DOI: 10.1080/13102818.2015.1047200] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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Llirós M, Inceoğlu Ö, García-Armisen T, Anzil A, Leporcq B, Pigneur LM, Viroux L, Darchambeau F, Descy JP, Servais P. Bacterial community composition in three freshwater reservoirs of different alkalinity and trophic status. PLoS One 2014; 9:e116145. [PMID: 25541975 PMCID: PMC4277477 DOI: 10.1371/journal.pone.0116145] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 12/03/2014] [Indexed: 11/21/2022] Open
Abstract
In order to investigate the factors controlling the bacterial community composition (BCC) in reservoirs, we sampled three freshwater reservoirs with contrasted physical and chemical characteristics and trophic status. The BCC was analysed by 16S rRNA gene amplicon 454 pyrosequencing. In parallel, a complete dataset of environmental parameters and phytoplankton community composition was also collected. BCC in the analysed reservoirs resembled that of epilimnetic waters of natural freshwater lakes with presence of Actinobacteria, Alpha- and Betaproteobacteria, Cytophaga–Flavobacteria–Bacteroidetes (CFB) and Verrucomicrobia groups. Our results evidenced that the retrieved BCC in the analysed reservoirs was strongly influenced by pH, alkalinity and organic carbon content, whereas comparatively little change was observed among layers in stratified conditions.
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Affiliation(s)
- Marc Llirós
- Laboratory of Freshwater Ecology, University of Namur, Namur, Belgium
| | - Özgül Inceoğlu
- Ecologie des Systèmes Aquatiques, Université Libre de Bruxelles, Brussels, Belgium
| | | | - Adriana Anzil
- Ecologie des Systèmes Aquatiques, Université Libre de Bruxelles, Brussels, Belgium
| | - Bruno Leporcq
- Laboratory of Freshwater Ecology, University of Namur, Namur, Belgium
| | | | - Laurent Viroux
- Laboratory of Freshwater Ecology, University of Namur, Namur, Belgium
| | | | - Jean-Pierre Descy
- Laboratory of Freshwater Ecology, University of Namur, Namur, Belgium
| | - Pierre Servais
- Ecologie des Systèmes Aquatiques, Université Libre de Bruxelles, Brussels, Belgium
- * E-mail:
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Borges AV, Morana C, Bouillon S, Servais P, Descy JP, Darchambeau F. Carbon cycling of Lake Kivu (East Africa): net autotrophy in the epilimnion and emission of CO2 to the atmosphere sustained by geogenic inputs. PLoS One 2014; 9:e109500. [PMID: 25314144 PMCID: PMC4196920 DOI: 10.1371/journal.pone.0109500] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Accepted: 09/11/2014] [Indexed: 11/19/2022] Open
Abstract
We report organic and inorganic carbon distributions and fluxes in a large (>2000 km2) oligotrophic, tropical lake (Lake Kivu, East Africa), acquired during four field surveys, that captured the seasonal variations (March 2007-mid rainy season, September 2007-late dry season, June 2008-early dry season, and April 2009-late rainy season). The partial pressure of CO2 (pCO2) in surface waters of the main basin of Lake Kivu showed modest spatial (coefficient of variation between 3% and 6%), and seasonal variations with an amplitude of 163 ppm (between 579±23 ppm on average in March 2007 and 742±28 ppm on average in September 2007). The most prominent spatial feature of the pCO2 distribution was the very high pCO2 values in Kabuno Bay (a small sub-basin with little connection to the main lake) ranging between 11,213 ppm and 14,213 ppm (between 18 and 26 times higher than in the main basin). Surface waters of the main basin of Lake Kivu were a net source of CO2 to the atmosphere at an average rate of 10.8 mmol m(-2) d(-1), which is lower than the global average reported for freshwater, saline, and volcanic lakes. In Kabuno Bay, the CO2 emission to the atmosphere was on average 500.7 mmol m(-2) d(-1) (∼46 times higher than in the main basin). Based on whole-lake mass balance of dissolved inorganic carbon (DIC) bulk concentrations and of its stable carbon isotope composition, we show that the epilimnion of Lake Kivu was net autotrophic. This is due to the modest river inputs of organic carbon owing to the small ratio of catchment area to lake surface area (2.15). The carbon budget implies that the CO2 emission to the atmosphere must be sustained by DIC inputs of geogenic origin from deep geothermal springs.
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Affiliation(s)
- Alberto V. Borges
- Chemical Oceanography Unit, Université de Liège, Liège, Belgium
- * E-mail:
| | - Cédric Morana
- Department of Earth and Environmental Sciences, KU Leuven, Leuven, Belgium
| | - Steven Bouillon
- Department of Earth and Environmental Sciences, KU Leuven, Leuven, Belgium
| | - Pierre Servais
- Ecologie des Systèmes Aquatiques, Université Libre de Bruxelles, Bruxelles, Belgium
| | - Jean-Pierre Descy
- Research Unit in Environmental and Evolutionary Biology, University of Namur, Namur, Belgium
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Tarbe AL, Unrein F, Stenuite S, Pirlot S, Sarmento H, Sinyinza D, Descy JP. Protist herbivory: a key pathway in the pelagic food web of Lake Tanganyika. Microb Ecol 2011; 62:314-323. [PMID: 21336683 DOI: 10.1007/s00248-011-9817-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2010] [Accepted: 01/30/2011] [Indexed: 05/30/2023]
Abstract
Herbivory and bacterivory by phagotrophic protists were estimated in the southern basin of the oligotrophic Lake Tanganyika at different seasons (in the rainy season in February-March 2007 and in the dry season in July-August 2006 and September 2007), using two independent methods: the selective inhibitor technique for assessing community grazing on picocyanobacteria (PCya) and fluorescently labelled bacteria (FLB) and Synechococcus (FLA) to estimate bacterivory and herbivory by phagotrophic nanoflagellates (NF) and ciliates. Protistan grazing impact on both heterotrophic bacteria and PCya was mainly due to NF, which contributed up to 96% of the microbial grazing. There was a clear selection of FLA by protists. PCya represented the main carbon source for both flagellates and ciliates in the mixolimnion, accounting for an average of 83% of the total carbon obtained from the ingestion of picoplanktonic organisms. Protists were the main consumers of particulate primary production (46-74% depending on season). Significant seasonal variation of grazing rates (0.011-0.041 h(-1)) was found, chiefly following variation of PCya production and biomass. Assuming a growth efficiency of 0.4, total protozoan production varied seasonally (189-313 g C m(-2) day(-1)) and was roughly half of particulate phytoplankton production. This study provides evidence that NF and PCya were tightly coupled in Lake Tanganyika and that herbivory by protists may be one of the reasons why this great lake has high productivity. Our results bring support to the idea that microbial herbivory is a major process in oligotrophic freshwater systems.
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Affiliation(s)
- Anne-Laure Tarbe
- Laboratory of Freshwater Ecology, Department of Biology, University of Namur, rue de Bruxelles 61, 5000, Namur, Belgium
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Pigneur LM, Marescaux J, Roland K, Etoundi E, Descy JP, Van Doninck K. Phylogeny and androgenesis in the invasive Corbicula clams (Bivalvia, Corbiculidae) in Western Europe. BMC Evol Biol 2011; 11:147. [PMID: 21619630 PMCID: PMC3126740 DOI: 10.1186/1471-2148-11-147] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Accepted: 05/27/2011] [Indexed: 11/15/2022] Open
Abstract
Background The genus Corbicula is one of the most invasive groups of molluscs. It includes both sexual and androgenetic lineages. The present study re-assessed the different morphotypes and haplotypes of West European Corbicula in order to clarify their taxonomic identification and phylogenetic relationships with American and Asian Corbicula clams. We studied several populations from West European river basins (Meuse, Seine, Rhine and Rhône) through an "integrative taxonomy" approach. We combined morphology, partial mitochondrial COI and cyt b sequences and eleven microsatellite loci. Furthermore, we looked for discrepancies between mtDNA and nrDNA/morphology, indicative of androgenesis between lineages. Results There are three Corbicula morphotypes in Western Europe associated to three mitochondrial lineages and three genotypes. Form R shares the same COI haplotype as the American form A and the Japanese C. leana. Form S and the American form C have the same haplotype, although their morphologies seem divergent. The European form Rlc belongs to the same mitochondrial lineage as both the American form B and the Asian C. fluminea. Interestingly, within each haplotype/genotype or lineage, no genetic diversity was found although their invasive success is high. Moreover, we detected rare mismatches between mtDNA and nrDNA/morphology, indicative of androgenesis and mitochondrial capture between form R and form S and therefore challenging the phylogenetic relatedness and the species status within this genus. The global phylogenetic analysis revealed that the sexual Corbicula lineages seem restricted to the native areas while their androgenetic relatives are widespread and highly invasive. Conclusions We clarified the discrepancies and incongruent results found in the literature about the European morphotypes of Corbicula and associated mitochondrial lineages. The three West European morphotypes belong to three distinct nuclear and mitochondrial lineages. However mitochondrial capture occurs in sympatric populations of forms R and S. The species status of the morphotypes therefore remains doubtful. Moreover the androgenetic lineages seem widely distributed compared to their sexual relatives, suggesting that androgenesis and invasive success may be linked in the genus Corbicula.
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Affiliation(s)
- Lise-Marie Pigneur
- Research Unit in Environmental and Evolutionary Biology, University of Namur, Belgium.
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Rooke JC, Vandoorne B, Léonard A, Meunier CF, Cambier P, Sarmento H, Descy JP, Su BL. Prolonging the lifetime and activity of silica immobilised Cyanidium caldarium. J Colloid Interface Sci 2011; 356:159-64. [DOI: 10.1016/j.jcis.2011.01.020] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2010] [Revised: 01/06/2011] [Accepted: 01/06/2011] [Indexed: 11/26/2022]
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Rooke JC, Léonard A, Sarmento H, Meunier CF, Descy JP, Su BL. Novel photosynthetic CO2bioconvertor based on green algae entrapped in low-sodium silica gels. ACTA ACUST UNITED AC 2011. [DOI: 10.1039/c0jm02712j] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Rooke JC, Léonard A, Meunier CF, Sarmento H, Descy JP, Su BL. Hybrid photosynthetic materials derived from microalgae Cyanidium caldarium encapsulated within silica gel. J Colloid Interface Sci 2009; 344:348-52. [PMID: 20138290 DOI: 10.1016/j.jcis.2009.12.053] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2009] [Revised: 12/17/2009] [Accepted: 12/19/2009] [Indexed: 11/19/2022]
Abstract
Cyanidium caldarium (Tilden) Geitler SAG 16.91 has been encapsulated within a porous silica host structure to target novel photosynthetic hybrid materials suitable for use in solar cells or CO(2) fixation. C. caldarium cells are both thermophilic and acidophilic; on account of these tolerances the hybrid materials could be employed in more extreme heat conditions. TEM highlights that the external cell membrane can remain intact after encapsulation. The images reveal an alignment of silica gel around the external membrane of the cell, providing evidence that the cell wall acts as both a nucleation and polymerisation site for silica species and that the silica scaffold formed by the aggregation of colloidal particles, generates a porosity that can facilitate the transport of nutrients towards the cell. Epifluorescence microscopy and UV-visible spectroscopy have revealed the preservation of photosynthetic apparatus post-immobilisation. Productivity studies showed how the presence of silica nanoparticles within the matrix can adversely interact with the exterior cellular structures preventing the production of oxygen through photosynthesis.
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Affiliation(s)
- Joanna Claire Rooke
- Laboratoire de Chimie des Matériaux Inorganiques, The University of Namur (FUNDP), 61 Rue de Bruxelles, B-5000 Namur, Belgium
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Rooke JC, Léonard A, Sarmento H, Descy JP, Su BL. Photosynthesis within porous silica gel: viability and activity of encapsulated cyanobacteria. ACTA ACUST UNITED AC 2008. [DOI: 10.1039/b802705f] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Abstract
Bacterial mortality was studied using two complementary methods between 2002 and 2004 in the two main basins (north and south) of Lake Tanganyika. The disappearance of radioactivity from the DNA of natural assemblages of bacteria previously labeled with tritiated thymidine was used to estimate the mortality due to grazing by predators (72%) and due to the cell lysis (28%). Measurements of ingestion rate of bacteria by protozoa using fluorescent micro-particles yielded protozoan grazing rates similar to those provided by the thymidine method, and showed that heterotrophic nano-flagellates were responsible for most of the grazing pressure on the bacterial community of the pelagic zone (92-99%). Bacterial cell lysis was the second process involved in bacterial mortality, ranking before ciliate grazing. Overall, bacterial mortality was balanced with bacterial production. With regard to the assessment of the trophic role of bacteria, it was estimated that c. 5-8% of the organic carbon taken up by bacteria was converted into protozoan biomass and was thus available for metazoans.
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Affiliation(s)
- Samuel Pirlot
- Laboratory of Freshwater Ecology, URBO, Department of Biology, University of Namur, Namur, Belgium
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De Wever A, Muylaert K, Van der Gucht K, Pirlot S, Cocquyt C, Descy JP, Plisnier PD, Vyverman W. Bacterial community composition in Lake Tanganyika: vertical and horizontal heterogeneity. Appl Environ Microbiol 2005; 71:5029-37. [PMID: 16151083 PMCID: PMC1214687 DOI: 10.1128/aem.71.9.5029-5037.2005] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2004] [Accepted: 03/29/2005] [Indexed: 11/20/2022] Open
Abstract
Vertical and latitudinal differences in bacterial community composition (BCC) in Lake Tanganyika were studied during the dry season of 2002 by means of denaturing gradient gel electrophoresis analysis of PCR-amplified 16S RNA fragments. Dominant bands were sequenced and identified as members of the Cyanobacteria, Actinobacteria, Nitrospirae, green nonsulfur bacteria, and Firmicutes divisions and the Gamma- and Deltaproteobacteria subdivisions. The BCC in the lake displayed both vertical and latitudinal variation. Vertical changes in BCC were related to the thermal water column stratification, which influences oxygen and nutrient concentrations. Latitudinal variation was related to upwelling of deep water and increased primary production in the south of the lake. The number of bands per sample increased with bacterial production in the epilimnion of the lake, suggesting a positive diversity-productivity relationship.
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Affiliation(s)
- Aaike De Wever
- Ghent University, Department Biology, Section Protistology and Aquatic Ecology, 9000 Ghent, Belgium.
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Everbecq E, Gosselain V, Viroux L, Descy JP. Potamon: a dynamic model for predicting phytoplankton composition and biomass in lowland rivers. Water Res 2001; 35:901-912. [PMID: 11235885 DOI: 10.1016/s0043-1354(00)00360-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
POTAMON is a unidimensional, non-stationary model, designed for simulating potamoplankton from source to mouth. The forcing variables are discharge, river morphology, water temperature, available light and nutrient inputs. Given the description of several algal categories, POTAMON allows to simulate algal "successions" at a particular site, as well as longitudinal changes of potamoplankton composition and biomass. The algal categories differ by their physiology, their loss rates, and their sensitivity to grazing by zooplankton. Two zooplankton categories were considered, Brachionus-like and Keratella-like, which differ by their clearance rate, their incipient limiting level, their selectivity towards phytoplankton, and their growth yield. The model simulates satisfactorily the onset and the magnitude of the phytoplankton spring bloom in the Belgian part of R. Meuse, the biomass decrease in early summer, and the autumn bloom. It also renders the major variations of algal assemblages along the river. The model allows to confirm that the main driving variables of potamoplankton dynamics in a eutrophic river are physical factors: discharge and related variables (e.g. retention time), light and temperature. In addition, the simulations confirm that the zooplankton-phytoplankton interaction may result in phytoplankton biomass fluctuations and compositional changes. POTAMON can be useful to explore plankton dynamics in a large river, and it may become a tool to test various management measures.
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Affiliation(s)
- E Everbecq
- Centre for Environmental Study and Modelling, University of Liège, Belgium
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