[en] During this study, we investigated the seasonal variability of the concentration and the stable isotope composition of several inorganic and organic matter (OM) reservoirs in the large, oligotrophic and deep tropical Lake Kivu (East Africa). Data were acquired over 1 year at a fortnightly temporal resolution. The _13C signature of the dissolved inorganic carbon (DIC) increased linearly with time during the rainy season, then suddenly decreased during the dry season due to vertical mixing with 13C-depleted DIC waters. The _13C signature of the particulate organic carbon pool (POC) revealed the presence of a consistently abundant methanotrophic biomass in the oxycline throughout the year. We also noticed a seasonal shift during the dry season toward higher values in the _15N of particulate nitrogen (PN) in the mixed layer and _15N-PN was significantly related to the contribution of cyanobacteria to the phytoplankton assemblage, suggesting that rainy season conditions could be more favourable to atmospheric nitrogen-fixing cyanobacteria. Finally, zooplankton were slightly enriched in 13C compared to the autochthonous POC pool, and the _15N signature of zooplankton followed well the seasonal variability in _15N-PN, consistently 3.0_1.1‰heavier than the PN pool. Together, _13C and _15N analysis suggests that zooplankton directly incorporate algal-derived OM in their biomass, and that they rely almost exclusively on this source of OM throughout the year in general agreement with the very low allochthonous OM inputs from rivers in Lake Kivu.
Research Center/Unit :
FOCUS - Freshwater and OCeanic science Unit of reSearch - ULiège
Disciplines :
Aquatic sciences & oceanology
Author, co-author :
Morana, Cédric ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Chemical Oceanography Unit (COU)
Darchambeau, François ; Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Océanographie chimique
Roland, Fleur ; Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Océanographie chimique
Borges, Alberto ; Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Océanographie chimique
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, doi: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, doi: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, doi: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-Yildiz, Y., Altabet, M. A., Yilmaz, A., and Tuʇrul, 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 δ18O 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 carbonisotope fractionation during aqueous photosynthesis: A paleopCO2barometer, 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.
Lesutiene, J., Bukaveckas, P. A., Gasiu¯naite, Z. R., Pilkaityte, 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, doi: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, doi: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, doi: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, doi: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, doi: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, doi: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.
