Articles | Volume 12, issue 16
19 Aug 2015
Research article | 19 Aug 2015
Biogeochemistry of a large and deep tropical lake (Lake Kivu, East Africa: insights from a stable isotope study covering an annual cycle
C. Morana et al.
C. Morana, A. V. Borges, F. A. E. Roland, F. Darchambeau, J.-P. Descy, and S. Bouillon
Biogeosciences, 12, 2077–2088,
Vao Fenotiana Razanamahandry, Marjolein Dewaele, Gerard Govers, Liesa Brosens, Benjamin Campforts, Liesbet Jacobs, Tantely Razafimbelo, Tovonarivo Rafolisy, and Steven Bouillon
Biogeosciences, 19, 3825–3841,Short summary
In order to shed light on possible past vegetation shifts in the Central Highlands of Madagascar, we measured stable isotope ratios of organic carbon in soil profiles along both forested and grassland hillslope transects in the Lake Alaotra region. Our results show that the landscape of this region was more forested in the past: soils in the C4-dominated grasslands contained a substantial fraction of C3-derived carbon, increasing with depth.
Rey Harvey Suello, Simon Lucas Hernandez, Steven Bouillon, Jean-Philippe Belliard, Luis Dominguez-Granda, Marijn Van de Broek, Andrea Mishell Rosado Moncayo, John Ramos Veliz, Karem Pollette Ramirez, Gerard Govers, and Stijn Temmerman
Biogeosciences, 19, 1571–1585,Short summary
This research shows indications that the age of the mangrove forest and its position along a deltaic gradient (upstream–downstream) play a vital role in the amount and sources of carbon stored in the mangrove sediments. Our findings also imply that carbon capture by the mangrove ecosystem itself contributes partly but relatively little to long-term sediment organic carbon storage. This finding is particularly relevant for budgeting the potential of mangrove ecosystems to mitigate climate change.
Man Zhao, Liesbet Jacobs, Steven Bouillon, and Gerard Govers
Biogeosciences, 18, 1511–1523,Short summary
We investigate the relative importance of two individual factors (hydrodynamical disturbance and aquatic microbial community) that possibly control SOC decomposition rates in river systems. We found aquatic microbial organisms led to rapid SOC decomposition, while effect of mechanical disturbance is relative minor. We propose a simple conceptual model: hydrodynamic disturbance is only important when soil aggregates are strong enough to withstand the disruptive forces imposed by water immersions.
Samuel T. Wilson, Alia N. Al-Haj, Annie Bourbonnais, Claudia Frey, Robinson W. Fulweiler, John D. Kessler, Hannah K. Marchant, Jana Milucka, Nicholas E. Ray, Parvadha Suntharalingam, Brett F. Thornton, Robert C. Upstill-Goddard, Thomas S. Weber, Damian L. Arévalo-Martínez, Hermann W. Bange, Heather M. Benway, Daniele Bianchi, Alberto V. Borges, Bonnie X. Chang, Patrick M. Crill, Daniela A. del Valle, Laura Farías, Samantha B. Joye, Annette Kock, Jabrane Labidi, Cara C. Manning, John W. Pohlman, Gregor Rehder, Katy J. Sparrow, Philippe D. Tortell, Tina Treude, David L. Valentine, Bess B. Ward, Simon Yang, and Leonid N. Yurganov
Biogeosciences, 17, 5809–5828,Short summary
The oceans are a net source of the major greenhouse gases; however there has been little coordination of oceanic methane and nitrous oxide measurements. The scientific community has recently embarked on a series of capacity-building exercises to improve the interoperability of dissolved methane and nitrous oxide measurements. This paper derives from a workshop which discussed the challenges and opportunities for oceanic methane and nitrous oxide research in the near future.
Cédric Morana, Steven Bouillon, Vimac Nolla-Ardèvol, Fleur A. E. Roland, William Okello, Jean-Pierre Descy, Angela Nankabirwa, Erina Nabafu, Dirk Springael, and Alberto V. Borges
Biogeosciences, 17, 5209–5221,Short summary
A growing body of studies challenges the paradigm that methane (CH4) production occurs only under anaerobic conditions. Our field experiments revealed that oxic CH4 production is closely related to phytoplankton metabolism and is indeed a common feature in five contrasting African lakes. Nevertheless, we found that methanotrophic activity in surface waters and CH4 emissions to the atmosphere were predominantly fuelled by CH4 generated in sediments and physically transported to the surface.
Clare Woulds, James B. Bell, Adrian G. Glover, Steven Bouillon, and Louise S. Brown
Biogeosciences, 17, 1–12,Short summary
Sedimented hydrothermal vents occur where heated, mineral-rich (hydrothermal) water seeps through seafloor sediments. They host chemosynthetic microbes, which use chemical energy to fix dissolved carbon dioxide into sugars (chemosynthesis). We conducted carbon tracing experiments, and observed chemosynthesis at both vent and non-vent sites. Thus, chemosynthesis occurred over a much larger area than expected, suggesting it is more widespread than previously thought.
Alberto V. Borges, François Darchambeau, Thibault Lambert, Cédric Morana, George H. Allen, Ernest Tambwe, Alfred Toengaho Sembaito, Taylor Mambo, José Nlandu Wabakhangazi, Jean-Pierre Descy, Cristian R. Teodoru, and Steven Bouillon
Biogeosciences, 16, 3801–3834,Short summary
Tropical rivers might be strong sources of CO2 and CH4 to the atmosphere, although there is an enormous data gap. The origin of CO2 in lowland tropical rivers is not well characterized and can be from terra firme or from wetlands (flooded forests and aquatic macrophytes). We obtained a large field dataset of CO2, CH4 and N2O in the Congo, the second-largest river in the world, which allows us to quantity the emission of these greenhouse gases to the atmosphere and investigate their origin.
Gwenaël Abril and Alberto V. Borges
Biogeosciences, 16, 769–784,Short summary
Based on classical concepts in ecology, and a literature survey, we highlight the importance of flooded land as a preferential source of atmospheric carbon to aquatic systems at the global scale. Studies in terrestrial and aquatic ecosystems could be reconciled by considering the occurrence of an efficient wetland CO2 pump to river systems. New methodological approaches coupling hydrology and ecology are also necessary to improve scientific knowledge on carbon fluxes at the land–water interface.
Samuel T. Wilson, Hermann W. Bange, Damian L. Arévalo-Martínez, Jonathan Barnes, Alberto V. Borges, Ian Brown, John L. Bullister, Macarena Burgos, David W. Capelle, Michael Casso, Mercedes de la Paz, Laura Farías, Lindsay Fenwick, Sara Ferrón, Gerardo Garcia, Michael Glockzin, David M. Karl, Annette Kock, Sarah Laperriere, Cliff S. Law, Cara C. Manning, Andrew Marriner, Jukka-Pekka Myllykangas, John W. Pohlman, Andrew P. Rees, Alyson E. Santoro, Philippe D. Tortell, Robert C. Upstill-Goddard, David P. Wisegarver, Gui-Ling Zhang, and Gregor Rehder
Biogeosciences, 15, 5891–5907,Short summary
To determine the variability between independent measurements of dissolved methane and nitrous oxide, seawater samples were analyzed by multiple laboratories. The results revealed the influences of the different parts of the analytical process, from the initial sample collection to the calculation of the final concentrations. Recommendations are made to improve dissolved methane and nitrous oxide measurements to help preclude future analytical discrepancies between laboratories.
Trent R. Marwick, Fredrick Tamooh, Bernard Ogwoka, Alberto V. Borges, François Darchambeau, and Steven Bouillon
Biogeosciences, 15, 1683–1700,Short summary
A 2-year biogeochemical record provides annual sediment and element flux estimates for the non-dammed Sabaki River, Kenya, establishing a baseline for future research in light of impending construction of the first major upstream reservoir. Over 80 % of material fluxes occur across the wet season, with annual yields comparable to the adjacent, and dammed, Tana River. Observations at low-flow periods suggest large mammalian herbivores may be vectors of terrestrial subsidies to the water column.
Alberto V. Borges, Gwenaël Abril, and Steven Bouillon
Biogeosciences, 15, 1093–1114,Short summary
The Mekong River is among the largest on Earth and is vital for the economy of Vietnam and South East Asia and the livelihood of the local population (70 million across six countries). Numerous dams for hydropower are planned, which will affect the delivery of water and sediments to the Mekong delta, with numerous possible consequences. We report the dynamics of two greenhouse gases (CO2 and CH4) in the Mekong delta that can be used as a reference state to evaluate future changes.
Naomi Geeraert, Fred O. Omengo, Fredrick Tamooh, Trent R. Marwick, Alberto V. Borges, Gerard Govers, and Steven Bouillon
Manuscript not accepted for further reviewShort summary
We observed that the relationship between the concentrations and the water discharge in the Tana River changed in wet seasons with and without flooding. Detailed sampling in those seasons is required in order to construct several rating curves and to obtain reliable flux estimates. The sediment and carbon fluxes in function of discharge will help us to asses the flux changes that can be expected when the hydrology changes due to climate change or human impact.
Thibault Lambert, Steven Bouillon, François Darchambeau, Philippe Massicotte, and Alberto V. Borges
Biogeosciences, 13, 5405–5420,Short summary
This paper aims to investigate the spatial variability in dissolved organic matter (DOM) in terms of both concentration and composition in the Congo River network. Stable carbon isotopes and absorption and fluorescent properties of DOM were used as proxies for DOM composition. This study shows that DOM degradation within the Congo Basin results in the transition from aromatic to aliphatic DOM as well as the role of landscape and water residence time on this transition.
Clare Woulds, Steven Bouillon, Gregory L. Cowie, Emily Drake, Jack J. Middelburg, and Ursula Witte
Biogeosciences, 13, 4343–4357,Short summary
Estuarine sediments are important locations for carbon cycling and burial. We used tracer experiments to investigate how site conditions affect the way in which seafloor biological communities cycle carbon. We showed that while total respiration rates are primarily determined by temperature, total carbon processing by the biological community is strongly related to its biomass. Further, we saw a distinct pattern of carbon cycling in sandy sediment, in which uptake by bacteria dominates.
Fleur A. E. Roland, François Darchambeau, Cédric Morana, Sean A. Crowe, Bo Thamdrup, and Alberto V. Borges
Manuscript not accepted for further reviewShort summary
We studied methane consumption in a tropical Great Lake (Lake Kivu, East Africa). Lake Kivu has huge methane concentrations in its deep anoxic waters, but is a very poor emitter of methane to the atmosphere, which suppose a strong methane consumption in the water column. During this study, we put in evidence high aerobic and anaerobic consumption rates, whose relative importance varied with the season (higher aerobic rates in dry season, when the oxic compartment is wider).
Thibault Lambert, Cristian R. Teodoru, Frank C. Nyoni, Steven Bouillon, François Darchambeau, Philippe Massicotte, and Alberto V. Borges
Biogeosciences, 13, 2727–2741,Short summary
This manuscript presents a detailed analysis of transport and transformation of dissolved organic matter along the Zambezi River and its largest tributary. A particular focus is put on the effects of floodplains/wetlands and reservoirs as well as low-flow vs. high-flow conditions on the longitudinal patterns in DOM concentration and composition. It is the first study to present such a detailed analysis for a whole, large river system, and in particular for a tropical river other than the Amazon.
N. Geeraert, F. O. Omengo, G. Govers, and S. Bouillon
Biogeosciences, 13, 517–525,Short summary
Rivers transport a large amount of carbon as dissolved organic carbon (DOC). Our incubation experiments on water of the Tana River, Kenya, showed that microbial decomposition of 10–60 % of the initial DOC occurred within the first 24–48 h. Simultaneously, there was a decrease in isotopic composition, indicating that DOC derived from C4 vegetation is preferentially decomposed. This has implications for the assessment of vegetation in a catchment based on isotope signatures of riverine carbon.
C. R. Teodoru, F. C. Nyoni, A. V. Borges, F. Darchambeau, I. Nyambe, and S. Bouillon
Biogeosciences, 12, 2431–2453,Short summary
CO2 and CH4 concentrations and fluxes in the Zambezi River basin are well below the median/average values reported previously for tropical rivers, streams and reservoirs, and mainly controlled by the connectivity with floodplains and the presence of waterfalls and man-made reservoirs. The mass balance suggests that carbon transport to the ocean represents the major component (~60%) of the budget, while emissions to the atmosphere account for less than 40% of the total carbon yield.
C. Morana, A. V. Borges, F. A. E. Roland, F. Darchambeau, J.-P. Descy, and S. Bouillon
Biogeosciences, 12, 2077–2088,
M. Hagens, C. P. Slomp, F. J. R. Meysman, D. Seitaj, J. Harlay, A. V. Borges, and J. J. Middelburg
Biogeosciences, 12, 1561–1583,Short summary
This study looks at the combined impacts of hypoxia and acidification, two major environmental stressors affecting coastal systems, in a seasonally stratified basin. Here, the surface water experiences less seasonality in pH than the bottom water despite higher process rates. This is due to a substantial reduction in the acid-base buffering capacity of the bottom water as it turns hypoxic in summer. This highlights the crucial role of the buffering capacity as a modulating factor in pH dynamics.
G. Abril, S. Bouillon, F. Darchambeau, C. R. Teodoru, T. R. Marwick, F. Tamooh, F. Ochieng Omengo, N. Geeraert, L. Deirmendjian, P. Polsenaere, and A. V. Borges
Biogeosciences, 12, 67–78,Short summary
We compared pCO2 data calculated from pH and alkalinity from those measured directly in a large array of temperate and tropical freshwaters. This revealed a large overestimation (up to 300%) of calculated pCO2 in the case of acidic and organic-rich waters, due to a contribution of organic acids anions to alkalinity and a lower buffering capacity of the carbonate system at acidic pH. Given the widespread distribution of acidic freshwaters, direct measurements of water pCO2 are encouraged.
P. Ciais, A. J. Dolman, A. Bombelli, R. Duren, A. Peregon, P. J. Rayner, C. Miller, N. Gobron, G. Kinderman, G. Marland, N. Gruber, F. Chevallier, R. J. Andres, G. Balsamo, L. Bopp, F.-M. Bréon, G. Broquet, R. Dargaville, T. J. Battin, A. Borges, H. Bovensmann, M. Buchwitz, J. Butler, J. G. Canadell, R. B. Cook, R. DeFries, R. Engelen, K. R. Gurney, C. Heinze, M. Heimann, A. Held, M. Henry, B. Law, S. Luyssaert, J. Miller, T. Moriyama, C. Moulin, R. B. Myneni, C. Nussli, M. Obersteiner, D. Ojima, Y. Pan, J.-D. Paris, S. L. Piao, B. Poulter, S. Plummer, S. Quegan, P. Raymond, M. Reichstein, L. Rivier, C. Sabine, D. Schimel, O. Tarasova, R. Valentini, R. Wang, G. van der Werf, D. Wickland, M. Williams, and C. Zehner
Biogeosciences, 11, 3547–3602,
W. Thiery, A. Martynov, F. Darchambeau, J.-P. Descy, P.-D. Plisnier, L. Sushama, and N. P. M. van Lipzig
Geosci. Model Dev., 7, 317–337,
T. R. Marwick, F. Tamooh, B. Ogwoka, C. Teodoru, A. V. Borges, F. Darchambeau, and S. Bouillon
Biogeosciences, 11, 443–460,
F. Tamooh, A. V. Borges, F. J. R. Meysman, K. Van Den Meersche, F. Dehairs, R. Merckx, and S. Bouillon
Biogeosciences, 10, 6911–6928,
Related subject area
Biogeochemistry: LimnologyRapidly increasing sulfate concentration: a hidden promoter of eutrophication in shallow lakesThe dominant role of sunlight in degrading winter dissolved organic matter from a thermokarst lake in a subarctic peatlandContrasting activation energies of respiration and nutrient uptake drive lower ecosystem-level uptake at higher temperaturesDissolved organic matter signatures in urban surface waters: spatio-temporal patterns and driversTowards a history of Holocene P dynamics for the Northern Hemisphere using lake sediment geochemical recordsMethane in the Danube Delta: the importance of spatial patterns and diel cycles for atmospheric emission estimatesMethane oxidation in the waters of a humic-rich boreal lake stimulated by photosynthesis, nitrite, Fe(III) and humicsPorewater δ13CDOC indicates variable extent of degradation in different talik layers of coastal Alaskan thermokarst lakesHolocene phototrophic community and anoxia dynamics in meromictic Lake Jaczno (NE Poland) using high-resolution hyperspectral imaging and HPLC dataChanging sources and processes sustaining surface CO2 and CH4 fluxes along a tropical river to reservoir systemThe relative importance of photodegradation and biodegradation of terrestrially derived dissolved organic carbon across four lakes of differing trophic statusThe influences of historic lake trophy and mixing regime changes on long-term phosphorus fraction retention in sediments of deep eutrophic lakes: a case study from Lake Burgäschi, SwitzerlandIce formation on lake surfaces in winter causes warm-season bias of lacustrine brGDGT temperature estimatesDrivers of diffusive CH4 emissions from shallow subarctic lakes on daily to multi-year timescalesHigh organic carbon burial but high potential for methane ebullition in the sediments of an Amazonian hydroelectric reservoirDirect O2 control on the partitioning between denitrification and dissimilatory nitrate reduction to ammonium in lake sedimentsSpatial distribution of environmental indicators in surface sediments of Lake Bolshoe Toko, Yakutia, RussiaOstracods as ecological and isotopic indicators of lake water salinity changes: the Lake Van exampleReviews and syntheses: Dams, water quality and tropical reservoir stratificationNitrogen cycling in Sandusky Bay, Lake Erie: oscillations between strong and weak export and implications for harmful algal bloomsDistinctive effects of allochthonous and autochthonous organic matter on CDOM spectra in a tropical lakeHigh-frequency productivity estimates for a lake from free-water CO2 concentration measurementsNitrification and ammonium dynamics in Taihu Lake, China: seasonal competition for ammonium between nitrifiers and cyanobacteriaQuality transformation of dissolved organic carbon during water transit through lakes: contrasting controls by photochemical and biological processesContinuous measurement of air–water gas exchange by underwater eddy covarianceCapturing temporal and spatial variability in the chemistry of shallow permafrost pondsOrganic carbon mass accumulation rate regulates the flux of reduced substances from the sediments of deep lakesCyanobacterial carbon concentrating mechanisms facilitate sustained CO2 depletion in eutrophic lakesNew insights on resource stoichiometry: assessing availability of carbon, nitrogen, and phosphorus to bacterioplanktonSpatio-seasonal variability of chromophoric dissolved organic matter absorption and responses to photobleaching in a large shallow temperate lakeIsotopic composition of nitrate and particulate organic matter in a pristine dam reservoir of western India: implications for biogeochemical processesBacterial production in subarctic peatland lakes enriched by thawing permafrostPhotochemical mineralisation in a boreal brown water lake: considerable temporal variability and minor contribution to carbon dioxide productionAre flood-driven turbidity currents hot spots for priming effect in lakes?Organic carbon burial efficiency in a subtropical hydroelectric reservoirImportance of within-lake processes in affecting the dynamics of dissolved organic carbon and dissolved organic and inorganic nitrogen in an Adirondack forested lake/watershedTemperature dependence of the relationship between pCO2 and dissolved organic carbon in lakesThe nature of organic carbon in density-fractionated sediments in the Sacramento-San Joaquin River Delta (California)Microbial nutrient limitation in Arctic lakes in a permafrost landscape of southwest GreenlandPhototrophic pigment diversity and picophytoplankton in permafrost thaw lakesCarbon dynamics in highly heterotrophic subarctic thaw pondsImpact of forest harvesting on water quality and fluorescence characteristics of dissolved organic matter in eastern Canadian Boreal Shield lakes in summerSpatial distribution and sources of organic carbon in the surface sediment of Bosten Lake, ChinaHuman land uses enhance sediment denitrification and N2O production in Yangtze lakes primarily by influencing lake water qualityThermal processes of thermokarst lakes in the continuous permafrost zone of northern Siberia – observations and modeling (Lena River Delta, Siberia)Thermokarst lake methanogenesis along a complete talik profileSeasonal dynamics of organic carbon and metals in thermokarst lakes from the discontinuous permafrost zone of western SiberiaMethanotrophy within the water column of a large meromictic tropical lake (Lake Kivu, East Africa)The effects of river inflow and retention time on the spatial heterogeneity of chlorophyll and water–air CO2 fluxes in a tropical hydropower reservoirPartial coupling and differential regulation of biologically and photochemically labile dissolved organic carbon across boreal aquatic networks
Chuanqiao Zhou, Yu Peng, Li Chen, Miaotong Yu, Muchun Zhou, Runze Xu, Lanqing Zhang, Siyuan Zhang, Xiaoguang Xu, Limin Zhang, and Guoxiang Wang
Biogeosciences, 19, 4351–4360,Short summary
The dramatical increase in SO42- concentration up to 100 mg L-1 in eutrophic lakes has aroused great attention. It enhanced the sulfate reduction to release a large amount of ΣS2- during cyanobacteria decomposition. The Fe2+ released from the iron reduction process is captured by ΣS2-, and finally the combination of iron and P was reduced, promoting the release of endogenous P. Therefore, increasing sulfate concentrations are shown to be a hidden promoter of eutrophication in shallow lakes.
Flora Mazoyer, Isabelle Laurion, and Milla Rautio
Biogeosciences, 19, 3959–3977,Short summary
Dissolved organic matter collected at the end of winter from a peatland thermokarst lake was highly transformed and degraded by sunlight, leading to bacterial stimulation and CO2 production, but a fraction was also potentially lost by photoflocculation. Over 18 days, 18 % of the incubated dissolved organic matter was lost under sunlight, while dark bacterial degradation was negligible. Sunlight could have a marked effect on carbon cycling in organic-rich thermokarst lakes after ice-off.
Nathan Tomczyk, Amy Rosemond, Anna Kaz, and Jonathan Benstead
Revised manuscript accepted for BGShort summary
Warming is expected to increase rates of microbial metabolism, but the effect of warming on nutrient demand is unclear. Our experiments demonstrate that microbial nutrient uptake increases less with temperature than metabolism, particularly when environmental nutrient concentrations are low. However, our simulation models suggest that warming may actually lead to declines in ecosystem-scale nutrient uptake as warming accelerates the depletion of carbon substrates required for microbial growth.
Clara Romero González-Quijano, Sonia Herrero Ortega, Peter Casper, Mark O. Gessner, and Gabriel A. Singer
Biogeosciences, 19, 2841–2853,Short summary
Despite today's diversity of methods to measure dissolved organic matter (DOM), its potential to give ecological information about urban surface waters has been underused. We found DOM from urban lakes and ponds to differ greatly from that of urban streams and rivers in composition as well as temporal turnover. Urban land use (the percentage of green space), nutrient supply and point source pollution were the principal drivers of DOM. We suggest including DOM composition in regular monitoring.
Madeleine Moyle, John F. Boyle, and Richard C. Chiverrell
Biogeosciences, 18, 5609–5638,Short summary
We reconstruct Holocene landscape P yield and lake water TP concentration for 24 sites across the Northern Hemisphere by applying a process model to published lake sediment geochemical records. We find sites with the same landscape development history show similar geochemical profiles depending on climate, human impact, and other local factors. Our reconstructions can be used to understand present-day terrestrial P cycling, lake water nutrient status, and export of terrestrial P to the oceans.
Anna Canning, Bernhard Wehrli, and Arne Körtzinger
Biogeosciences, 18, 3961–3979,Short summary
Inland waters are usually not well restrained in terms of greenhouse gas measurements. One of these regions is the Danube Delta, Romania. Therefore, we measured continuously with sensors to collect high-resolution data for CH4 and O2 throughout the Delta. We found significant variation for all concentrations over the day and night and between regions, as well as large spatial variation throughout all regions, with large CH4 concentrations flowing in from the reed beds to the lakes.
Sigrid van Grinsven, Kirsten Oswald, Bernhard Wehrli, Corinne Jegge, Jakob Zopfi, Moritz F. Lehmann, and Carsten J. Schubert
Biogeosciences, 18, 3087–3101,Short summary
Lake Lovojärvi is a nutrient-rich lake with high amounts of methane at the bottom, but little near the top. Methane comes from the sediment and rises up through the water but is consumed by microorganisms along the way. They use oxygen if available, but in deeper water layers, no oxygen was present. There, nitrite, iron and humic substances were used, besides a collaboration between photosynthetic organisms and methane consumers, in which the first produced oxygen for the latter.
Ove H. Meisel, Joshua F. Dean, Jorien E. Vonk, Lukas Wacker, Gert-Jan Reichart, and Han Dolman
Biogeosciences, 18, 2241–2258,Short summary
Arctic permafrost lakes form thaw bulbs of unfrozen soil (taliks) beneath them where carbon degradation and greenhouse gas production are increased. We analyzed the stable carbon isotopes of Alaskan talik sediments and their porewater dissolved organic carbon and found that the top layers of these taliks are likely more actively degraded than the deeper layers. This in turn implies that these top layers are likely also more potent greenhouse gas producers than the underlying deeper layers.
Stamatina Makri, Andrea Lami, Luyao Tu, Wojciech Tylmann, Hendrik Vogel, and Martin Grosjean
Biogeosciences, 18, 1839–1856,Short summary
Anoxia in lakes is a major growing concern. In this study we applied a multiproxy approach combining high-resolution hyperspectral imaging (HSI) pigment data with specific HPLC data to examine the Holocene evolution and main drivers of lake anoxia and trophic state changes. We find that when human impact was low, these changes were driven by climate and natural lake-catchment evolution. In the last 500 years, increasing human impact has promoted lake eutrophication and permanent anoxia.
Cynthia Soued and Yves T. Prairie
Biogeosciences, 18, 1333–1350,Short summary
Freshwater reservoirs emit greenhouse gases (GHGs, CO2 and CH4) to the atmosphere; however, the sources underlying these emissions are numerous, and their magnitude is not well known. This study quantifies surface CO2 and CH4 emissions and all their potential sources in a tropical reservoir. Results highlight the changes in GHG sources along the river–reservoir continuum, with internal metabolism being a key component but highly uncertain and challenging to estimate at an ecosystem scale.
Christopher M. Dempsey, Jennifer A. Brentrup, Sarah Magyan, Lesley B. Knoll, Hilary M. Swain, Evelyn E. Gaiser, Donald P. Morris, Michael T. Ganger, and Craig E. Williamson
Biogeosciences, 17, 6327–6340,Short summary
We looked at how terrestrial dissolved organic carbon (DOC) from the watersheds of four different lakes responded to both biodegradation (i.e., microbes) and photodegradation (i.e., sunlight). The traditional paradigm is that biodegradation is more important than photodegradation. Our research shows that, on short timescales (i.e., 7 d), sunlight is more important than microbes in degrading DOC. Interestingly, the lakes had different responses to sunlight based on their trophic status.
Luyao Tu, Paul Zander, Sönke Szidat, Ronald Lloren, and Martin Grosjean
Biogeosciences, 17, 2715–2729,Short summary
In a small, deep lake on the Swiss Plateau, net fluxes of labile P fractions in sediments that can be released to surface waters have been predominately controlled by past hypolimnetic anoxic conditions since the early 1900s. More than 40 years of hypolimnetic withdrawal can effectively reduce net P fluxes in sediments and internal P loads but not effectively decrease eutrophication. These findings should likely serve the management of deep eutrophic lakes in temperate zones.
Jiantao Cao, Zhiguo Rao, Fuxi Shi, and Guodong Jia
Biogeosciences, 17, 2521–2536,Short summary
BrGDGT distribution in Gonghai Lake is different from surrounding soils, and its derived temperature reflects a mean annual lake water temperature (LWT) that is higher than the mean annual air temperature (AT). The higher mean annual LWT is due to ice formation in winter that prevents thermal exchange between lake water and air.
Joachim Jansen, Brett F. Thornton, Alicia Cortés, Jo Snöälv, Martin Wik, Sally MacIntyre, and Patrick M. Crill
Biogeosciences, 17, 1911–1932,Short summary
Lakes are important emitters of the greenhouse gas methane. We use field observations and a model to evaluate the importance of known drivers of methane production and release. Fast and slow changes of the diffusive flux were governed by wind speed and sediment temperature, respectively. Increased turbulence enhanced release, but storms depleted the lakes of gas and limited emissions. Our findings may inform model studies on the effects of weather and climate change on lake methane emissions.
Gabrielle R. Quadra, Sebastian Sobek, José R. Paranaíba, Anastasija Isidorova, Fábio Roland, Roseilson do Vale, and Raquel Mendonça
Biogeosciences, 17, 1495–1505,Short summary
Hydropower is expanding in the Amazon Basin, but the potential effects of river damming on carbon fluxes cannot be gauged due to a lack of studies. We quantified, for the first time in an Amazonian reservoir, both organic carbon burial and the concentrations of methane in the sediments. We found that the dual role of sediments as both a carbon sink and methane source may be particularly pronounced in this Amazonian reservoir.
Adeline N. Y. Cojean, Jakob Zopfi, Alan Gerster, Claudia Frey, Fabio Lepori, and Moritz F. Lehmann
Biogeosciences, 16, 4705–4718,Short summary
Our results demonstrate the importance of oxygen in regulating the fate of nitrogen (N) in the sediments of Lake Lugano south basin, Switzerland. Hence, our study suggests that, by changing oxygen concentration in bottom waters, the seasonal water column turnover may significantly regulate the partitioning between N removal and N recycling in surface sediments, and it is likely that a similar pattern can be expected in a wide range of environments.
Boris K. Biskaborn, Larisa Nazarova, Lyudmila A. Pestryakova, Liudmila Syrykh, Kim Funck, Hanno Meyer, Bernhard Chapligin, Stuart Vyse, Ruslan Gorodnichev, Evgenii Zakharov, Rong Wang, Georg Schwamborn, Hannah L. Bailey, and Bernhard Diekmann
Biogeosciences, 16, 4023–4049,Short summary
To better understand time-series data in lake sediment cores in times of rapidly changing climate, we study within-lake spatial variabilities of environmental indicator data in 38 sediment surface samples along spatial habitat gradients in the boreal deep Lake Bolshoe Toko (Russia). Our methods comprise physicochemical as well as diatom and chironomid analyses. Species diversities vary according to benthic niches, while abiotic proxies depend on river input, water depth, and catchment lithology.
Jeremy McCormack, Finn Viehberg, Derya Akdemir, Adrian Immenhauser, and Ola Kwiecien
Biogeosciences, 16, 2095–2114,Short summary
We juxtapose changes in ostracod taxonomy, morphology (noding) and oxygen (δ18O) and carbon (δ13C) isotopic composition for the last 150 kyr with independent low-resolution salinity proxies. We demonstrate that for Lake Van, salinity is the most important factor influencing the composition of the ostracod assemblage and the formation of nodes on the valves of limnocytherinae species. Ostracod δ18O shows a higher sensibility towards climatic and hydrological variations than the bulk isotopy.
Robert Scott Winton, Elisa Calamita, and Bernhard Wehrli
Biogeosciences, 16, 1657–1671,Short summary
A global boom in dam construction throughout the world’s tropics motivated us to review and synthesize information on the water quality impacts of dams with a focus on low-latitude contexts and scope for mitigation. Sediment trapping and reservoir stratification are key process driving chemical and ecological impacts on tropical rivers. We analyze the 54 most-voluminous low-latitude reservoirs and find that stratification seems to be a ubiquitous phenomenon.
Kateri R. Salk, George S. Bullerjahn, Robert Michael L. McKay, Justin D. Chaffin, and Nathaniel E. Ostrom
Biogeosciences, 15, 2891–2907,Short summary
This paper highlights dynamic nitrogen cycling in a freshwater estuary, with implications for harmful algal blooms and downstream nitrogen loading. Phytoplankton and microbes actively consumed nitrogen in this system, contributing to recycling of nitrogen within the system and permanent nitrogen removal, respectively. However, delivery of nitrogen from the river and fixation of atmospheric nitrogen by phytoplankton outweighed nitrogen uptake, resulting in variable downstream nitrogen delivery.
Luciana Pena Mello Brandão, Ludmila Silva Brighenti, Peter Anton Staehr, Eero Asmala, Philippe Massicotte, Denise Tonetta, Francisco Antônio Rodrigues Barbosa, Diego Pujoni, and José Fernandes Bezerra-Neto
Biogeosciences, 15, 2931–2943,Short summary
Using mesocosms we investigated the effect of the increase in the allochthonous and autochthonous sources of DOM in a tropical lake, in order to simulate its effects on the characteristics of lakes caused by anthropogenic impacts. The seasonal allochthonous input has much larger effects on the lake and, in addition to increasing nutrients, alters the transparency of water and consequently controls the seasonal dynamics of phytoplankton (autochthonous source) and lake ecology.
Maria Provenzale, Anne Ojala, Jouni Heiskanen, Kukka-Maaria Erkkilä, Ivan Mammarella, Pertti Hari, and Timo Vesala
Biogeosciences, 15, 2021–2032,Short summary
We extensively tested and refined a direct, high-frequency free-water CO2 measurement method to study the lake net ecosystem productivity. The method was first proposed in 2008, but neglected ever since. With high-frequency direct methods, we can calculate the lake productivity more precisely, and parameterise its dependency on environmental variables. This helps us expand our knowledge on the carbon cycle in the water, and leads to a better integration of water bodies in carbon budgets.
Justyna J. Hampel, Mark J. McCarthy, Wayne S. Gardner, Lu Zhang, Hai Xu, Guangwei Zhu, and Silvia E. Newell
Biogeosciences, 15, 733–748,Short summary
Our paper highlights the importance of dual-nutrient management: nitrogen (N) and phosphorus (P) in lakes with cyanobacterial harmful algal blooms. Taihu Lake (China) experiences seasonal blooms due to increased input of N and P from field runoff. The main process investigated in our study, nitrification, is important for N removal through denitrification. We show that nitrification is less efficient during the blooms, due to competition for nutrients between N microbes and cyanobacteria.
Martin Berggren, Marcus Klaus, Balathandayuthabani Panneer Selvam, Lena Ström, Hjalmar Laudon, Mats Jansson, and Jan Karlsson
Biogeosciences, 15, 457–470,Short summary
The quality of dissolved organic carbon (DOC), especially its color, is a defining feature of freshwater ecosystems. We found that colored DOC fractions are surprisingly resistant to natural degradation during water transit through many brown-water lakes. This is explained by the dominance of microbial processes that appear to selectively remove noncolored DOC. However, in lakes where sunlight degradation plays a relatively larger role, significant DOC bleaching occurs.
Peter Berg and Michael L. Pace
Biogeosciences, 14, 5595–5606,Short summary
We use the aquatic eddy covariance technique – developed first for benthic O2 flux measurements – right below the air–water interface (~ 4 cm) to determine gas exchange rates and coefficients. This use of the technique is particularly useful in studies of gas exchange and its dynamics and controls. The approach can thus help reduce the recognized problem of large uncertainties linked to gas exchange estimates in traditional aquatic ecosystem studies.
Matthew Q. Morison, Merrin L. Macrae, Richard M. Petrone, and LeeAnn Fishback
Biogeosciences, 14, 5471–5485,Short summary
Shallow ponds and lakes are common features in permafrost systems. We show that the chemistry of these water bodies can be dynamic, although the changes are consistent through time between ponds. This synchrony in some water chemistry appears to be related to water level variations. Because hydrological conditions can vary greatly over the course of the year and during a storm, this work underscores the importance of interpreting water samples from these systems within their hydrologic context.
Thomas Steinsberger, Martin Schmid, Alfred Wüest, Robert Schwefel, Bernhard Wehrli, and Beat Müller
Biogeosciences, 14, 3275–3285,Short summary
Based on a broad dataset of lake sediment analysis and porewater measurements from various Swiss lakes, this paper argues that the accumulation of organic carbon in the sediment is one of the main driving forces for the generation of reduced substances such as methane and ammonia. These substances significantly contribute to the hypolimnetic oxygen consumption. The relationships presented help to evaluate the scale of the flux of reduced substances where no direct measurements are available.
Ana M. Morales-Williams, Alan D. Wanamaker Jr., and John A. Downing
Biogeosciences, 14, 2865–2875,Short summary
Our study investigated the mechanisms sustaining cyanobacteria blooms when CO2 is depleted in lake surface waters. We found that when lake CO2 concentrations drop below those of the atmosphere, cyanobacteria switch on carbon concentrating mechanisms (CCMs), allowing them to actively take up bicarbonate. This may provide bloom-forming cyanobacteria with a competitive advantage over other algae. These results provide insight into the timing and duration of blooms in high-nutrient lakes.
Ana R. A. Soares, Ann-Kristin Bergström, Ryan A. Sponseller, Joanna M. Moberg, Reiner Giesler, Emma S. Kritzberg, Mats Jansson, and Martin Berggren
Biogeosciences, 14, 1527–1539,
María Encina Aulló-Maestro, Peter Hunter, Evangelos Spyrakos, Pierre Mercatoris, Attila Kovács, Hajnalka Horváth, Tom Preston, Mátyás Présing, Jesús Torres Palenzuela, and Andrew Tyler
Biogeosciences, 14, 1215–1233,Short summary
As first study within my PhD with the general objective to improve and adapt remote sensing algorithms for the estimation of coloured dissolved organic matter (CDOM) content in lakes in a global scale, we carried out this set of measurements and experiments. This study gives us a better understanding of sources and variability in the optical properties of CDOM in lakes and how photobleaching controls and affects them.
Pratirupa Bardhan, Syed Wajih Ahmad Naqvi, Supriya G. Karapurkar, Damodar M. Shenoy, Siby Kurian, and Hema Naik
Biogeosciences, 14, 767–779,Short summary
Although India has the third highest number of dams globally, there is a knowledge gap on the cycling of bioessential elements in such systems. This study (first of its kind) investigates the stable isotopes of nitrate and particulate organic matter in a pristine Indian reservoir. Nitrogen transformations in the anaerobic bottom waters were isotopically characterised. Overall, solar intensity, water depth and redox conditions are the major controls on the biogeochemical cycling in this system.
Bethany N. Deshpande, Sophie Crevecoeur, Alex Matveev, and Warwick F. Vincent
Biogeosciences, 13, 4411–4427,Short summary
Subarctic lakes are changing in size as a result of permafrost thawing, resulting in mobilization of soil materials. Our study characterizes the carbon and nutrient regime of a set of thaw lakes and their adjacent permafrost soils in a rapidly degrading landscape, showing how these materials create favorable conditions for aquatic bacterial communities. We discuss the controls over the bacterial community, and demonstrate that gain processes are not a primary control.
Marloes Groeneveld, Lars Tranvik, Sivakiruthika Natchimuthu, and Birgit Koehler
Biogeosciences, 13, 3931–3943,Short summary
Temporal variability in the apparent quantum yield of photochemical CDOM mineralisation in a boreal brown water lake was severalfold smaller than previously reported across different lakes. Simulated DIC photoproduction (2012–2014) averaged 2.0 ± 0.1 to 10.3 ± 0.7 g C m−2 yr−1 using the least and most reactive sample, which represented 1 to 8 % of the total mean CO2 emissions. Thus, direct CDOM photomineralisation makes only a minor contribution to mean CO2 emissions from Swedish brown water lakes.
Damien Bouffard and Marie-Elodie Perga
Biogeosciences, 13, 3573–3584,Short summary
This survey of an exceptional flood over Lake Geneva challenges the long-standing hypothesis that dense, particle-loaded and oxygenated rivers plunging into lakes necessarily contribute to deep-oxygen replenishment. We identified some river intrusions as hot spots for oxygen consumption, where inputs of fresh river-borne organic matter reactivate the respiration of more refractory lacustrine organic matter in a process referred to as "priming effect".
Raquel Mendonça, Sarian Kosten, Sebastian Sobek, Simone Jaqueline Cardoso, Marcos Paulo Figueiredo-Barros, Carlos Henrique Duque Estrada, and Fábio Roland
Biogeosciences, 13, 3331–3342,Short summary
Hydroelectric reservoirs in the tropics emit greenhouse gases but also bury carbon in their sediments. We investigated the efficiency of organic carbon (OC) burial in a large tropical reservoir, using spatially resolved measurements of sediment accumulation, and found that more than half (~ 57 %) of the OC deposited onto the sediment is buried. This high efficiency in OC burial indicates that tropical reservoirs may bury OC more efficiently than natural lakes.
Phil-Goo Kang, Myron J. Mitchell, Patrick J. McHale, Charles T. Driscoll, Shreeram Inamdar, and Ji-Hyung Park
Biogeosciences, 13, 2787–2801,Short summary
Lakes play important roles in controlling organic matter derived from watersheds and within-lake production. The organic matter is normally measured by elemental quantities, such as carbon(C) and nitrogen(N), because the two elements are essential for aquatic ecosystems. We observed an decrease of C, but an increase of N in organic matters in a lake. The reason of the different pattern might be that inorganic N in the lake appeared to be recycled to produce organic N due to within-lake processes.
L. Pinho, C. M. Duarte, H. Marotta, and A. Enrich-Prast
Biogeosciences, 13, 865–871,Short summary
Unlike the positive relationship reported before between partial pression of carbon dioxide and dissolved organic carbon for lake waters, we found no significant relationship in our low-latitude lakes, despite very broad ranges in both variables. The strength of this relationship declines with increasing water temperature, suggesting substantial differences in carbon cycling in warm lakes, which must be considered when upscaling limnetic carbon cycling to global scales.
S. G. Wakeham and E. A. Canuel
Biogeosciences, 13, 567–582,Short summary
Bed sediments from the Sacramento-San Joaquin River Delta (CA) were fractionated according to density and analyzed for sediment mass distribution, elemental (C and N) composition, mineral surface area, and stable carbon and radiocarbon isotope compositions of organic carbon (OC) and fatty acids to evaluate the nature of organic carbon in river sediments. These data demonstrate the complex source and age distributions within river sediments.
B. Burpee, J. E. Saros, R. M. Northington, and K. S. Simon
Biogeosciences, 13, 365–374,Short summary
This study investigates microbial nutrient limitation patterns across a region of southwest Greenland in relation to environmental factors. Using microbial enzyme activities to infer nutrient limitation patterns, we determined that most lakes are P-limited. Further, P limitation was tightly controlled by lake dissolved organic carbon (DOC) concentration.
A. Przytulska, J. Comte, S. Crevecoeur, C. Lovejoy, I. Laurion, and W. F. Vincent
Biogeosciences, 13, 13–26,Short summary
Permafrost thaw lakes are a subject of increasing research interest given their abundance across the northern landscape. Our aim in the present study was to characterize the photosynthetic communities in a range of subarctic thaw lakes using a combination of HPLC analysis of algal and bacterial pigments, flow cytometry and molecular analysis. Our results showed that the thaw lakes contain diverse phototrophic communities and are a previously unrecognized habitat for abundant picophotoautotrophs.
T. Roiha, I. Laurion, and M. Rautio
Biogeosciences, 12, 7223–7237,Short summary
Global warming thaws permafrost and accelerates the formation of thaw ponds in subarctic and arctic regions. These abundant ponds receive large terrestrial carbon inputs from the thawing and eroding permafrost, which is mainly used by bacterioplankton for the production of new biomass. Bacteria metabolism also produces high levels of CO2 and CH4, which make thaw ponds important sources of greenhouse gases to the atmosphere. We present carbon dynamics in thaw ponds in northern Quebec.
P. Glaz, J.-P. Gagné, P. Archambault, P. Sirois, and C. Nozais
Biogeosciences, 12, 6999–7011,Short summary
In this study, we showed that logging activities have a short-term impact (1 year after the perturbation) on water quality in boreal Eastern Canadian Shield lakes. However, this effect seems to mitigate 2 years after the perturbation. Further, the analysis of the absorbance and fluorescence data showed that while DOC concentrations did significantly increase in perturbed lakes, the DOM quality did not measurably change.
Z. T. Yu, X. J. Wang, E. L. Zhang, C. Y. Zhao, and X. Q. Liu
Biogeosciences, 12, 6605–6615,Short summary
Bosten Lake is the largest inland freshwater lake in China, which has been impacted by land use changes, with implications for carbon burial. Our study showed a large spatial variability in total organic carbon (TOC) (1.8–4.4%); 54–90% of TOC was from autochthonous sources. Higher TOC content was found in the east and central-north sections and near the mouth of the Kaidu River, which was attributable to allochthonous, autochthonous plus allochthonous, and autochthonous sources, respectively.
W. Liu, L. Yao, Z. Wang, Z. Xiong, and G. Liu
Biogeosciences, 12, 6059–6070,
J. Boike, C. Georgi, G. Kirilin, S. Muster, K. Abramova, I. Fedorova, A. Chetverova, M. Grigoriev, N. Bornemann, and M. Langer
Biogeosciences, 12, 5941–5965,Short summary
We show that lakes in northern Siberia are very efficient with respect to energy absorption and mixing using measurements as well as numerical modeling. We show that (i) the lakes receive substantial energy for warming from net short-wave radiation; (ii) convective mixing occurs beneath the ice cover, follow beneath the ice cover, following ice break-up, summer, and fall (iii) modeling suggests that the annual mean net heat flux across the bottom sediment boundary is approximately zero.
J. K. Heslop, K. M. Walter Anthony, A. Sepulveda-Jauregui, K. Martinez-Cruz, A. Bondurant, G. Grosse, and M. C. Jones
Biogeosciences, 12, 4317–4331,Short summary
The relative magnitude of thermokarst lake CH4 production in surface sediments vs. deeper-thawed permafrost is not well understood. We assessed CH4 production potentials from a lake sediment core and adjacent permafrost tunnel in interior Alaska. CH4 production was highest in the organic-rich surface lake sediments and recently thawed permafrost at the bottom of the talik, implying CH4 production is highly variable and that both modern and ancient OM are important to lake CH4 production.
R. M. Manasypov, S. N. Vorobyev, S. V. Loiko, I. V. Kritzkov, L. S. Shirokova, V. P. Shevchenko, S. N. Kirpotin, S. P. Kulizhsky, L. G. Kolesnichenko, V. A. Zemtzov, V. V. Sinkinov, and O. S. Pokrovsky
Biogeosciences, 12, 3009–3028,Short summary
A year-around hydrochemical study (including full winter freezing and spring flood) of shallow thermokarst lakes from a discontinuous permafrost zone of western Siberia revealed conceptually new features of element concentration evolution over different seasons within a large scale of the lake size.
C. Morana, A. V. Borges, F. A. E. Roland, F. Darchambeau, J.-P. Descy, and S. Bouillon
Biogeosciences, 12, 2077–2088,
F. S. Pacheco, M. C. S. Soares, A. T. Assireu, M. P. Curtarelli, F. Roland, G. Abril, J. L. Stech, P. C. Alvalá, and J. P. Ometto
Biogeosciences, 12, 147–162,Short summary
CO2 fluxes in Funil Reservoir (FR) is driven by primary production and river inflow dynamics. Our findings suggest that the lack of spatial data in reservoir C budget calculations can affect regional and global estimates. Our results support the idea that the FR is a dynamic system where the hydrodynamics represented by changes in the river inflow and retention time are potentially a more important force driving both the Chl and pCO2 spatial variability than the in-system ecological factors.
J.-F. Lapierre and P. A. del Giorgio
Biogeosciences, 11, 5969–5985,
Adams, T. S. and Sterner, R. W.: The effect of dietary nitrogen content on trophic level 15N enrichment, Limnol. Oceanogr., 45, 601–607, 2000.
Alin, S. R. and Johnson, T. C.: Carbon cycling in large lakes of the world: A synthesis of production, burial, and lake-atmosphere exchange estimates, Global Biogeochem. Cy., 21, GB3002, https://doi.org/10.1029/2006GB002881, 2007.
Bade, D. L., Carpenter, S. R., Cole, J. J., Hanson, P. C., and Hesslein, R. H.: Controls of δ13C-DIC in lakes: Geochemistry, lake metabolism, and morphometry, Limnol. Oceanogr., 49, 1160–1172, 2004.
Blees, J., Niemann, H., Wenk, C. B., Zopfi, J., Schubert, C. J., Kirf, M. K., Veronesi, M. L., Hitz, C., and Lehmann, M. F.: Micro-aerobic bacterial methane oxidation in the chemocline and anoxic water column of deep south-Alpine Lake Lugano (Switzerland), Limnol. Oceanogr., 59, 311–324, 2014.
Bootsma, H. A. and Hecky, R. E.: A comparative introduction to the biology and limnology of the African Great Lakes, J. Great Lakes Res., 29, 3–18, 2003.
Borges, A. V., Abril, G., Delille, B., Descy, J. P., and Darchambeau, F.: Diffusive methane emissions to the atmosphere from Lake Kivu (Eastern Africa), J. Geophys. Res., 116, G03032, https://doi.org/10.1029/2011JG001673, 2011.
Borges, A. V., Morana, C., Bouillon, S., Servais, P., Descy, J.-P., and 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, 9, e109500, https://doi.org/10.1371/journal.pone.0109500, 2014.
Castañeda, I. S., Werne, J. P., Johnson, T. C., and Filley, T. R.: Late Quaternary vegetation history of southeast Africa: the molecular isotopic record from Lake Malawi. Palaeogeography, Palaeoclimatology, Palaeoecology, 275, 100–112, 2009.
Castillo, M. M., Kling, G. W., and Allan. J. D.: Bottom-up controls on bacterial production in tropical lowland rivers, Limnol. Oceanogr., 48, 1466–1475, 2003.
Çoban-Yıldız, Y., Altabet, M. A., Yılmaz, A., and Tuğrul, S.: Carbon and nitrogen isotopic ratios of suspended particulate organic matter (SPOM) in the Black Sea water column, Deep-Sea Res. Pt. II, 53, 1875–1892, 2006.
Cole, J. J.: Aquatic microbiology for ecosystem scientists: new and recycled paradigms in ecological microbiology, Ecosystems, 2, 215–225, 1999.
Cotner, J. B., Johengen, T. H., and Biddanda, B. A.: Intense winter heterotrophic production stimulated by benthic resuspension, Limnol. Oceanogr., 45, 1672–1676, 2000.
Darchambeau, F., Sarmento, H., and Descy, J.-P.: Primary production in a tropical large lake: The role of phytoplankton composition, Sci. Total Environ., 473, 178–188, 2014.
Del Giorgio, P. A., Cole, J. J., and Cimbleris, A.: Respiration rates in bacteria exceed phytoplankton production in unproductive aquatic systems, Nature, 385, 148–151, 1997.
Descy, J.-P. and Sarmento, H.: Microorganisms of the East African Great Lakes and their response to environmental changes, Freshwater Reviews, 1, 59–73, 2008.
Descy, J.-P., Higgins, H. W., Mackey, D. J., Hurley, J. P., and Frost, T. M.: Pigment ratios and phytoplankton assessment in northern Wisconsin lakes, J. Phycol., 36, 274–286, 2000.
Duarte, C. M. and Prairie, Y. T.: Prevalence of heterotrophy and atmospheric CO2 emissions from aquatic ecosystems, Ecosystems, 8, 862–870, 2005.
Finlay, K., Leavitt, P. R., Patoine, A., and Wissel, B.: Magnitudes and controls of organic and inorganic carbon flux through a chain of hardwater lakes on the northern Great Plains, Limnol. Oceanogr., 55, 1551–1564, 2010.
Fogel, M. L. and Cifuentes, L. A.: Isotope fractionation during primary production, 73–98, in: Organic geochemistry, edited by: Engel, M. H. and Macko, S. A., Plenum Press, New York, 1993.
Gillikin, D. P. and Bouillon, S.: Determination of δ 18O of water and δ13C of dissolved inorganic carbon using a simple modification of an elemental analyser-isotope ratio mass spectrometer: an evaluation, Rapid Commun. Mass Sp., 21, 1475–1478, 2007.
Gran, G.: Determination of the equivalence point in potentiometric titrations. Part II, Analysis, 77, 661–671, 1952.
Grey, J., Jones, R. I., and Sleep, D.: Seasonal changes in the importance of the source of organic matter to the diet of zooplankton in Loch Ness, as indicated by stable isotope analysis, Limnol. Oceanogr., 46, 505–513, 2001.
Haberyan, K. A. and Hecky, R. E.: The late Pleistocene and Holocene stratigraphy and paleolimnology of Lakes Kivu and Tanganyika, Palaeogeogr. Palaeocl., 61, 169–197, 1987.
Hawley, N. and Lee, C. H.: Sediment resuspension and transport in Lake Michigan during the unstratified period, Sedimentology, 46, 791–805, 1999.
Hecky, R. E. and Kling, H. J.: Phytoplankton ecology of the great lakes in the rift valleys of Central Africa, Arch. Hydrobiol.-Beiheft Ergebnisse der Limnologie, 25, 197–228, 1987.
Herczeg, A. L.: A stable carbon isotope study of dissolved inorganic carbon cycling in a softwater lake, Biogeochemistry, 4, 231–263, 1987.
Hollander, D. J. and McKenzie, J. A.: CO2 control on carbon-isotope fractionation during aqueous photosynthesis: A paleo-pCO2 barometer, Geology, 19, 929–932, 1991.
Jansson, M., Bergström, A. K., Blomqvist, P., and Drakare, S.: Allochthonous organic carbon and phytoplankton/bacterioplankton production relationships in lakes, Ecology, 81, 3250–3255, 2000.
Kaningini, M.: Etude de la croissance, de la reproduction et de l'exploitation de Limnothrissa miodon au lac Kivu, bassin de Bukavu (Zaïre), PhD thesis, Facultés Universitaires Notre Dame de la Paix, Namur, Belgium, 1995.
Kankaala, P., Taipale, S., Grey, J., Sonninen, E., Arvola, L., and Jones, R. I.: Experimental δ13C evidence for a contribution of methane to pelagic food webs in lakes, Limnol. Oceanogr., 51, 2821–2827, 2006.
Lehmann, M. F., Bernasconi, S. M., McKenzie, J. A., Barbieri, A., Simona, M., and Veronesi, M.: Seasonal variation of the δ13C and δ15N of particulate and dissolved carbon and nitrogen in Lake Lugano: Constraints on biogeochemical cycling in a eutrophic lake, Limnol. Oceanogr., 49, 415–429, 2004.
Lehner, B. and Döll, P.: Development and validation of a global database of lakes, reservoirs and wetlands, J. Hydrol., 296, 1–22, 2004.
Lesutienė, J., Bukaveckas, P. A., Gasiūnaitė, Z. R., Pilkaitytė, R., and Razinkovas-Baziukas, A.: Tracing the isotopic signal of a cyanobacteria bloom through the food web of a Baltic Sea coastal lagoon. Estuar. Coast. Shelf Sci., 138, 47–56, 2014.
Lewis, W. M. J.: Tropical lakes: how latitude makes a difference, in: Perspectives Tropical Limnology, edited by: F. Schiemer and Boland, K. T., SPB Academic Publishing, Amsterdam, 43–64, 1996.
Llirós, M., Gich, F., Plasencia, A., Auguet, J. C., Darchambeau, F., Casamayor, E. O., Descy, J.-P., and Borrego, C.: Vertical distribution of ammonia-oxidizing crenarchaeota and methanogens in the epipelagic waters of Lake Kivu (Rwanda-Democratic Republic of the Congo), Appl. Environ. Microb., 76, 6853–6863, 2010.
Ludwig, W., Probst, J. L., and Kempe, S.: Predicting the oceanic input of organic carbon by continental erosion, Global Biogeochem. Cy., 10, 23–41, 1996.
Macko, S. A., Fogel, M. L., Hare, P. E., and Hoering, T. C.: Isotopic fractionation of nitrogen and carbon in the synthesis of amino acids by microorganisms, Chem. Geol., 65, 79–92, 1987.
Marcé, R., Obrador, B., Morguí, J.-A., Lluís Riera, J., López, P., and Armengol, J.: Carbonate weathering as a driver of CO2 supersaturation in lakes, Nature Geosci., 8, 107–111, 2015.
Masilya, P.: Ecologie alimentaire compare de Limnothrissa miodon et de Lamprichthys tanganicanus au lac Kivu (Afrique de l'Est), PhD thesis, Facultés Universitaires Notre Dame de la Paix, Namur, Belgium, 2011.
Meyers, P. A. and Eadie, B. J.: Sources, degradation and recycling of organic matter associated with sinking particles in Lake Michigan, Org. Geochem., 20, 47–56, 1993.
Millero, F. J., Graham, T. B., Huang, F., Bustos-Serrano, H., and Pierrot, D.: Dissociation constants of carbonic acid in sea water as a function of salinity and temperature, Mar. Chem., 100, 80–94, 2006.
Montoya, J. P., Carpenter, E. J., and Capone, D. G.: Nitrogen fixation and nitrogen isotope abundances in zooplankton of the oligotrophic North Atlantic, Limnol. Oceanogr., 47, 1617–1628, 2002.
Morana, C., Sarmento, H., Descy, J.-P., Gasol, J. M., Borges, A. V., Bouillon, S., and Darchambeau, F.: Production of dissolved organic matter by phytoplankton and its uptake by heterotrophic prokaryotes in large tropical lakes, Limnol. Oceanogr., 59, 1364–1375, 2014.
Morana, C., Borges, A. V., Roland, F. A. E., Darchambeau, F., Descy, J.-P., and Bouillon, S.: Methanotrophy within the water column of a large meromictic tropical lake (Lake Kivu, East Africa), Biogeosciences, 12, 2077–2088, https://doi.org/10.5194/bg-12-2077-2015, 2015.
Mugidde, R., Hecky, R. E., Hendzel, L. L., and Taylor, W. D.: Pelagic nitrogen fixation in Lake Victoria (East Africa), J. Great Lakes Res., 29, 76–88, 2003.
Pasche, N., Alunga, G., Mills, K., Muvundja, F., Ryves, D. B., Schurter, M., Wehrli, B., and Schmid, M.: Abrupt onset of carbonate deposition in Lake Kivu during the 1960s: response to recent environmental changes, J. Paleolimnol., 44, 931–946, 2010.
Pasche, N., Schmid, M., Vazquez, F., Schubert, C. J., Wüest, A., Kessler, J. D., Pack, M. A., Reeburgh, W. S., and Bürgmann, H.: Methane sources and sinks in Lake Kivu, J. Geophys. Res., 116, G03006, https://doi.org/10.1029/2011JG001690, 2011.
Post, D. M.: Using stable isotopes to estimate trophic position: models, methods, and assumptions, Ecology, 83, 703–718, 2002.
Prairie, Y. T., Bird, D. F., and Cole, J. J.: The summer metabolic balance in the epilimnion of southeastern Quebec lakes, Limnol. Oceanogr., 47, 316–321, 2002.
Sarmento, H.: New paradigms in tropical limnology: the importance of the microbial food web, Hydrobiologia, 686, 1–14, 2012.
Sarmento, H., Isumbisho, M., and Descy, J.-P.: Phytoplankton ecology of Lake Kivu (eastern Africa), J. Plankton Res., 28, 815–829, 2006.
Sarmento, H., Isumbisho, M., Stenuite, S., Darchambeau, F., Leporcq, B., and Descy, J.-P.: Phytoplankton ecology of Lake Kivu (eastern Africa): biomass, production and elemental ratios, Int. Ver. Theor. Angew., 30, 709–713, 2009.
Schelske, C. L. and Hodell, D. A.: Recent changes in productivity and climate of Lake Ontario detected by isotopic analysis of sediments, Limnol. Oceanogr., 36, 961–975, 1991.
Schmid, M., Halbwachs, M., Wehrli, B., and Wüest, A.: Weak mixing in Lake Kivu: new insights indicate increasing risk of uncontrolled gas eruption, Geochem. Geophy. Geosy., 6, Q07009, https://doi.org/10.1029/2004GC000892, 2005.
Sirevåg, R., Buchanan, B. B., Berry, J. A., and Troughton, J. H.: Mechanisms of CO2 fixation in bacterial photosynthesis studied by the carbon isotope fractionation technique, Arch. Microbiol., 112, 35–38, 1977.
Sobek, S., Tranvik, L. J., Prairie, Y. T., Kortelainen, P., and Cole, J. J.: Patterns and regulation of dissolved organic carbon: An analysis of 7,500 widely distributed lakes, Limnol. Oceanogr., 52, 1208–1219, 2007.
Stets, E. G., Striegl, R. G., Aiken, G. R., Rosenberry, D. O., and Winter, T. C.: Hydrologic support of carbon dioxide flux revealed by whole-lake carbon budgets, J. Geophys. Res., 114, G01008, https://doi.org/10.1029/2008JG000783, 2009.
Thiery, W., Martynov, A., Darchambeau, F., Descy, J.-P., Plisnier, P.-D., Sushama, L., and van Lipzig, N. P. M.: Understanding the performance of the FLake model over two African Great Lakes, Geosci. Model Dev., 7, 317–337, https://doi.org/10.5194/gmd-7-317-2014, 2014.
Urban, N. R., Auer, M. T., Green, S. A., Lu, X., Apul, D. S., Powell, K. D., and Bub, L.: Carbon cycling in Lake Superior, J. Geophys. Res.-Oceans, 110, C06S90, https://doi.org/10.1029/2003JC002230, 2005.
Wada, E. and Hattori, A.: Natural abundance of 15N in particulate organic matter in the North Pacific Ocean, Geochim. Cosmochim. Ac., 40, 249–251, 1976.
Weiss, R. F.: Determinations of carbon dioxide and methane by dual catalyst flame ionization chromatography and nitrous oxide by electron capture chromatography, J. Chromatogr. Sci., 19, 611–616, 1981.
Weyhenmeyer, G. A. and Karlsson, J.: Nonlinear response of dissolved organic carbon concentrations in boreal lakes to increasing temperatures, Limnol. Oceanogr., 54, 2513–2519, 2009.
Wright, S. W., Jeffrey, S. W., Mantoura, R. F. C., Llewellyn, C. A., Bjornland, T., Repeta, D., and Welschmeyer, N.: Improved HPLC method for the analysis of chlorophylls and carotenoids from marine phytoplankton, Mar. Ecol.-Prog. Ser., 77, 183–196, 1991.