[en] The processing of terrestrially derived dissolved organic matter (DOM) during downstream transport in fluvial networks is poorly understood. Here, we report a dataset of dissolved organic carbon (DOC) concentrations and DOM composition (stable carbon isotope ratios, absorption and fluorescence properties) acquired along a 1700 km transect in the middle reach of the Congo River Basin. Samples were collected in the mainstem and its tributaries during high water (HW) and falling water (FW) periods. DOC concentrations and DOM composition along the mainstem were found to differ between the two periods, because of a reduced lateral mixing between the central water masses of the Congo River and DOM-rich waters from tributaries and also likely because of a greater photodegradation during FW as water residence time (WRT) increased. Although the Cuvette Centrale wetland (one of the world’s largest flooded forest) continuously releases highly aromatic DOM in streams and rivers of the Congo Basin, the downstream transport of DOM was found to result in an along stream gradient from aromatic to aliphatic compounds. The characterization of DOM through parallel factor analysis (PARAFAC) suggests that this transition results from (1) the losses of aromatic compounds by photodegradation and (2) the production of aliphatic compounds by biological reworking of terrestrial DOM. Finally, this study highlights the critical importance of the river-floodplain connectivity in tropical rivers in controlling DOM biogeochemistry at large spatial scale and suggests that the degree of DOM processing during downstream transport is a function of landscape characteristics and WRT
Research center :
FOCUS - Freshwater and OCeanic science Unit of reSearch - ULiège
Disciplines :
Aquatic sciences & oceanology
Author, co-author :
Lambert, Thibault ; Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Chemical Oceanography Unit (AGO)
Bouillon, S.
Darchambeau, François ; Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Chemical Oceanography Unit (AGO)
Massicotte, P.
Borges, Alberto ; Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Chemical Oceanography Unit (AGO)
Language :
English
Title :
Shift in the chemical composition of dissolved organic matter in the Congo River network
Publication date :
28 September 2016
Journal title :
Biogeosciences
ISSN :
1726-4170
eISSN :
1726-4189
Publisher :
European Geosciences Union, Katlenburg-Lindau, Germany
Baines, S. B. and Pace, M. L.: The production of dissolved organic matter by phytoplankton and its importance to bacteria: patterns across marine and freshwater systems, Limnol. Oceanogr., 36, 1078-1090, 1991.
Bano, N., Moran, M. A., and Hodson, R. E.: Photochemical formation of labile organic matter from two components of dissolved organic carbon in a freshwater wetland, Aquat. Microb. Ecol., 16, 95-102, 1998.
Battin, T. J.: Dissolved organic matter and its optical properties in a blackwater tributary of the upper Oricono river, Venezuela, Org. Geochem., 28, 561-569, 1998.
Battin, T. J., Kaplan, L. A., Findlay, S., Hopkinson, C. S., Marti, E., Packman, A. I., Newbold, J. D., and Sabater, F.: Biophysical controls on organic carbon fluxes in fluvial networks, Nat. Geosci., 1, 95-100, 2008.
Berggren, M., Lapierre, J.-F., and del Giorgio, P. A.: Magnitude and regulation of bacterioplankton respiratory quotient across freshwater environmental gradients, ISME J., 6, 984-993, doi:10.1038/ismej.2011.157, 2012.
Bertilsson, S. and Jones, J. B.: Supply of dissolved organic matter to aquatic ecosystems: autochthonous sources, in: Aquatic ecosystems: interactivity of dissolved organic matter, edited by: Findlay, S. and Sinsabaugh, R. L., Academic Press, 3-24, 2003.
Besemer, K., Luef, B., Preiner, S., Eichberger, B., Agis, M., and Peduzzi, P.: Sources and composition of organic matter for bacterial growth in a large European river floodplain system (Danube, Austria), Org. Geochem., 40, 321-331, 2009.
Bontemps, S., Defourney, P., Van Bogaert, E., and Arino, O.: GLOBCOVER2009 Products Description and Validation Report. (ESA and UCLouvain), available at: http://due.esrin.esa.int/files/ GLOBCOVER2009-Validation-Report-2.2.pdf (last access: 15 September 2015), 2011.
Borcard, D., Gillet, F., and Legendre, P.: Numerical ecology with R, Springer New York, New York, 306 pp., doi:10.1007/978-1-4419-7976-6, 2011.
Borges, A. V., Darchambeau, F., Teodoru, C. R., Marwick, T. R., Tamooh, F., Geeraert, N., Omengo, F. O., Guerin, F., Lambert, T., Morana, C., Okuku, E., and Bouillon, S.: Globally significant greenhouse-gas emissions from African inland waters, Nat. Geosci., 8, 637-642, doi:10.1038/ngeo2486, 2015a.
Borges, A. V., Abril, G., Darchambeau, F., Teodoru, C. R., Deborde, J., Vidal, L. O., Lambert, T., and Bouillon, S.: Divergent biophysical controls of aquatic CO2 and CH4 in the Worlds two largest rivers; Scientific Reports, 5, 15614, doi:10.1038/srep15614, 2015b.
Bouillon, S., Yambele, A., Spencer, R. G. M., Gillikin, D. P., Hernes, P. J., Six, J., Merckx, R., and Borges, A. V.: Organic matter sources, fluxes and greenhouse gas exchange in the Oubangui River (Congo River basin), Biogeosciences, 9, 2045-2062, doi:10.5194/bg-9-2045-2012, 2012.
Bouillon, S., Yambele, A., Gillikin, D. P., Teodoru, C. R., Darchambeau, F., Lambert, T., and Borges, A. V.: Contrasting biogeochemical characteristics of the Oubangui River and tributaries (Congo River basin), Scientific Report, 4, 1-10, doi:10.1038/srep05402, 2014.
Bricquet, J. P.: Les ecoulements du Congo a Brazzaville et la spatialisation des apports, in Grands Bassins Fluviaux Peri-atlantiques, edited by: Olivry, J. C. and Boulegue, J., Inst. Fr. de Rech. Sci. pour le Dev. en Coop. (ORSTOM), Paris, 27-38, 1995.
Bwangoy, J.-R. B., Hansen, M. C., Roy, D. P., De Grandi, G., and Justice, C. O.: Wetland mapping in the Congo Basin using optical and radar remotely sensed data and derived topographical indices, Remote Sens. Environ., 114, 73-86, 2010.
Cawley, K. M., Wolski, P., Mladenov, N., and Jaffe, R.: Dissolved organic matter biogeochemistry along a transect of the Okavango delta, Bostwana, Wetlands, 32, 475-486, doi:10.1007/s13157-012-0281-0, 2012.
Coble, P. G., Lead, J., Baker, A., Reynolds, D. M., and Spencer, R. G. M.: Aquatic Organic Matter Fluorescence, NY: Cambridge University Press, New York, 375 pp., 2014.
Cole, J. J., Prairie, Y. T., Caraco, N. F., McDowell, W. H., Tranvik, L. J., Striegl, R. G., Duarte, C. M., Kortelainen, P., Downing, J. A., Middelburg, J. J., and Melack, J.: Plumbing the global carbon cycle: integrating inland waters into the terrestrial carbon budget, Ecosystems, 10, 171-184, 2007.
Cory, R. M., McKnight, D. M., Chin, Y. P., Miller, P., and Jaros, C. L.: Chemical characteristics of fulvic acids from Arctic surface waters: Microbial contributions and photochemical transformations, J. Geophys. Res.-Biogeo., 112, G04S51, doi:10.1029/2006JG000343, 2007.
Cory, R. M., Ward, C. P., Crump, B. C., and Kling, G. W.: Sunlight controls water column processing of carbon in arctic freshwaters, Science, 345, 925-928, doi:10.1126/science.1253119, 2014.
Cory, R. M., Harrold, K. H., Neilson, B. T., and Kling, G. W.: Controls on dissolved organic matter (DOM) degradation in a headwater stream: the influence of photochemical and hydrological conditions in determining light-limitation or substratelimitation of photo-degradation, Biogeosciences, 12, 6669-6685, doi:10.5194/bg-12-6669-2015, 2015.
Coynel, A., Seyler, P., Etcheber, H., Meybeck, M., and Orange, D.: Spatial and seasonal dynamics of total suspended sediment and organic carbon species in the Congo River, Global Biogeochem. Cy., 19, GB4019, doi:10.1029/2004GB002335, 2005.
Creed, I. F., McKnight, D., Pellerin, B. A., Green, M. B., Bergamaschi, B. A., Aiken, G. R., Burns, D. A., Findlay, S. E. G., Shanley, J. B., Striegl, R. G., Aulenbach, B. T., Clow, D. W., Laudon, H., McGlynn, B. L., McGuire, K. J., Smith, T. A., and Stackpoole, S. M.: The river as a chemostat: fresh perspectives on dissolved organic matter flowing down the river continuum, Can. J. Fish. Aquat. Sci., 72, 1272-1285, doi:10.1139/cjfas-2014-0400, 2015.
Descy, J. P., Darchambeau, F., Lambert, T., Stoyneva, M. P., Bouillon, S., and Borges, A. V.: Phytoplankton dynamics in the Congo River, Freshwater Biol., doi:10.1111/fwb.12851, in press, 2016.
Fasching, C., Behounek, B., Singer, G. A., and Battin, T. J.: Microbial degradation of terrigenous dissolved organic matter and potential consequences for carbon cycling in brown-water streams, Scientific Reports, 4, 4981, doi:10.1038/srep04981, 2014.
Fellman, J. B., Hood, E., and Spencer, R. G. M.: Fluorescence spectroscopy opens new windows into dissolved organic matter dynamics in freshwater ecosystems: A review, Limnol. Oceanogr., 55, 2452-2462, doi:10.4319/lo.2010.55.6.2452, 2010.
Guillemette, F. and del Giorgio, P. A.: Simultaneous consumption and production of fluorescent dissolved organic matter by lake bacterioplankton, Environ. Microbiol., 14, 1432-1443, 2012.
Hanley, K., Wollheim, W. M., Salisbury, J., Huntington, T., and Aiken, G.: Controls on dissolved organic carbon quantity and chemical character in temperate rivers of North America, Global Biogeochem. Cy., 27, 492-504, doi:10.1002/gbc.20044, 2013.
Helms, J. R., Stubbins, A., Ritchie, J. D., Minor, E. C., Kieber, D. J., and Mopper, K.: Absorption spectral slopes and slope ratios as indicators of molecular weight, source, and photobleaching of chromophoric dissolved organic matter, Limnol. Oceanogr., 53, 955-969, 2008.
Ishii, S. K. L. and Boyer, T. H.: Behavior of reoccurring parafac components in fluorescent dissolved organic matter in natural and engineered systems: A critical review, Environ. Sci. Technol. 46, 2006-2017, doi:10.1021/es2043504, 2012.
Jaffe, R., McKnight, D., Maie, N., Cory, R., McDowell, W. H., and Campbell, J. L.: Spatial and temporal variations in DOM composition in ecosystems: The importance of long-term monitoring of optical properties, J. Geophys. Res.-Biogeo., 113, G04032, doi:10.1029/2008jg000683, 2008.
Junk, W., Bayley, P. B., and Sparks, R. E.: The flood pulse concept in river-floodplain systems, Can. Spec. Publ. Fish. Aquat. Sci., 106, 110-127, 1989.
Kellerman, A. M., Kothawala, D. N., Dittmar, T., and Tranvik, L. J.: Persistence of dissolved organic matter in lakes related to its molecular characteristics, Nat. Geosci., 8, 454-457, doi:10.1038/ngeo2440, 2015.
Kothawala, D. N., Stedmon, C. A., Muller, R. A., Weyhenmeyer, G. A., Kohler, S. J., and Tranvik, L. J.: Controls of dissolved organic matter quality: Evidence from a large-scale boreal lake survey, Glob. Change Biol., 20, 1101-1114, doi:10.1111/gcb.12488, 2014.
Lambert, T., Pierson-Wickmann, A.-C., Gruau, G., Thibault, J. N., and Jaffrezic, A.: Carbon isotopes as tracers of dissolved organic carbon sources and water pathways in headwater catchments, J. Hydrol., 402, 228-238, doi:10.1016/j.jhydrol.2011.03.014, 2011.
Lambert, T., Darchambeau, F., Bouillon, S., Alhou, B., Mbega, J.-D., Teodoru, C. R., Nyoni, F. C., Massicotte, P., and Borges, A. V.: Landscape control on the spatial and temporal variability of chromophoric dissolved organic matter and dissolved organic carbon in large African rivers, Ecosystems, 18, 1224-1239, doi:10.1007/s10021-015-9894-5, 2015.
Lambert, T., Teodoru, C. R., Nyoni, F. C., Bouillon, S., Darchambeau, F., Massicotte, P., and Borges, A. V.: Along-stream transport and transformation of dissolved organic matter in a large tropical river, Biogeosciences, 13, 2727-2741, doi:10.5194/bg-13-2727-2016, 2016.
Lapierre, J.-F. and del Giorgio, P. A.: Partial coupling and differential regulation of biologically and photochemically labile dissolved organic carbon across boreal aquatic networks, Biogeosciences, 11, 5969-5985, doi:10.5194/bg-11-5969-2014, 2014.
Laraque, A., Bricquet, J. P., Pandi, A., and Olivry, J. C.: A review of material transport by the Congo River and its tributaries, Hydrol. Process., 23, 3216-3224, 2009.
Leenheer, J. and Croue, J.: Characterizing aquatic dissolved organic matter, Environ. Sci. Technol., 37, 18-26, 2003.
Lehner, B. and Doll, P.: Development and validation of a global database of lakes, reservoirs and wetlands, J. Hydrol., 296, 1-22, doi:10.1016/j.jhydrol.2004.03.028, 2004.
Lehner, B., Verdin, K., and Jarvis, A.: New global hydrography derived from space borne elevation data, Eos, 89, 93-94, doi:10.1029/2008EO100001, 2008.
Mann, P. J., Spencer, R. G. M., Dinga, B. J., Poulsen, J.R., Hernes, P.J., Fiske, G., Salter, M. E., Wang, Z. A., Hoering, K.A., Six, J., and Holmes, R. M.: The biogeochemistry of carbon across a gradient of streams and rivers within the Congo Basin. J. Geophys. Res.-Biogeo., 119, 687-702, 2014.
Marin-Spiotta, E., Gruley, K. E., Crawford, J., Atkinson, E. E., Miesel, J. R., Greene, S., Cardona-Correa, C., and Spencer, R. G. M.: Paradigm shifts in soil organic matter research affect interpretations of aquatic carbon cycling: transcending disciplinary and ecosystem boundaries, Biogeochemistry, 117, 279-297, doi:10.1007/s10533-013-9949-7, 2014.
Massicotte, P. and Frenette, J.-J.: Spatial connectivity in a large river system: resolving the sources and fate of dissolved organic matter, Ecol. Appl., 21, 2600-2617, 2011.
McKnight, D. M., Boyer, E. W., Westerhoff, P. K., Doran, P. T., Kulbe, T., and Andersen, D. T.: Spectrofluorometric characterization of dissolved organic matter for indication of precursor organic material and aromaticity, Limnol. Oceanogr., 46, 38-48, 2001.
Meybeck, M.: Riverine transport of atmospheric carbon: source, global typology and budget, Water Air Soil Poll., 70, 443-463, 1993.
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.
Moreira-Turcq, P., Seyler, P., Guyot, J. L., and Etcheber, H.: Exportation of organic carbon from the Amazon River and its main tributaries, Hydrol. Process., 17, 1329-1344, 2003.
Murphy, K. R., Stedmon, C. A., Graeber, D., and Bro, R.: Fluorescence spectroscopy and multi-way techniques, PARAFAC, Anal. Methods, 5, 6557-6566, 2013.
Neff, J. C., Finlay, J. C., Zimov, S. A., Davydov, S. P., Carrasco, J. J., Schuur, E. A. G., and Davydova, A. I.: Seasonal changes in the age and structure of dissolved organic carbon in Siberian rivers and streams, Geophys. Res. Lett., 33, L23401, doi:10.1029/2006GL028222, 2006.
Ohno, T.: Fluorescence inner-filtering correction for determining the humification index of dissolved organic matter, Environ. Sci. Technol., 36, 742-746, doi:10.1021/Es0155276, 2002.
Osburn, C. L., Retamal, L., and Vincent, W. F.: Photoreactivity of chromophoric dissolved organic matter transported by the Mackenzie River to the Beaufort Sea, Mar. Chem., 115, 10-20, doi:10.1016/j.marchem.2009.05.003, 2009.
Poole, G. C.: Stream hydrogeomorphology as a physical science basis for advances in stream ecology, J. N. Am. Benthol. Soc., 29, 12-25, 2010.
Raymond, P. A., Saiers, J. E., and Sobczak W. V.: Hydrological and biogeochemical controls on watershed dissolved organic matter transport: pulse-shunt concept, Ecology, 97, 5-16, doi:10.1890/14-1684.1, 2016.
Remington, S., Krusche, A., and Richey, J.: Effects of DOM photochemistry on bacterial metabolism and CO2 evasion during falling water in a humic and a whitewater river in the Brazilian Amazon, Biogeochemistry, 105, 185-200, doi:10.1007/s10533-010-9565-8, 2011.
Richardson, D. C., Newbold, J. D., Aufdenkampe, A. K., Taylor, P. G., and Kaplan, L. A.: Measuring heterotrophic respiration rates of suspended particulate organic carbon from stream ecosystems, Limnol. Oceanogr.-Meth., 11, 247-261, 2013.
Runge, J.: The Congo River, Central Africa in Large Rivers: Geomorpholgy and Management, edited by: Gupta, A., John Wiley and Sons, Ltd, 293-309, 2008.
Sanderman, J., Lohse, K. A., Baldock, J. A., and Amundson, R.: Linking soils and streams: sources and chemistry of dissolved organic matter in a small coastal watershed, Water Resour. Res., 45, W03418, doi:10.1029/2008WR006977, 2009.
Spencer, R. G. M., Stubbins, A., Hernes, P. J., Baker, A., Mopper, K., Aufdenkampe, A. K., Dyda, R. Y., Mwamba, V. L., Mangangu, A. M., Wabakanghanzi, J. N., and Six, J.: Photochemical degradation of dissolved organic matter and dissolved lignin phenols from the Congo River, J. Geophys. Res.-Biogeo., 114, G03010, doi:10.1029/2009jg000968, 2009.
Spencer, R. G. M., Hernes, P. J., Ruf, R., Baker, A., Dyda, R. Y., Stubbins, A., and Six, J.: Temporal controls on dissolved organic matter and lignin biogeochemistry in a pristine tropical river, Democratic Republic of Congo, J. Geophys. Res., 115, G03013, doi:10.1029/2009JG001180, 2010.
Spencer, R. G. M., Hernes, P. J., Aufdenkampe, A. K., Baker, A., Gulliver, P., Stubbins, A., Aiken, G. R., Dyda, R. Y., Butler, K. D., Mwamba, V. L., Mangangu, A. M., Wabakanghanzi, J. N., and Six, J.: An initial investigation into the organic matter biogeochemistry of the Congo River, Geochim. Cosmochim. Ac., 84, 614-627, 2012.
Stedmon, C. A. and Markager, S.: Resolving the variability in DOM fluorescence in a temperate estuary and its catchment unsing PARAFAC, Limnol. Oceanogr, 50, 686-697, 2005.
Stedmon, C. A., Markager, S., and Bro, R.: Tracing dissolved organic matter in aquatic environments using a new approach to fluorescence spectroscopy, Mar. Chem., 82, 239-254, doi:10.1016/s0304-4203(03)00072-0, 2003.
Strahler, A. N.: Quantitative analysis of watershed geomorphology, T. Am. Geophys. Un., 38, 913-920, 1957.
Stubbins, A., Lapierre, J. F., Berggren, M., Prairie, Y. T., Dittmar, T., and del Giorgio, P. A.: Whats in an EEM? Molecular signatures associated with dissolved organic fluorescence in boreal Canada, Environ Sci. Technol., 48, 10598-10606, 2014.
Tranvik, L. J. and Bertilsson, S.: Contrasting effects of solar UV radiation on dissolved organic sources for bacterial growth, Ecol. Lett., 4, 458-463, 2001.
Vannote, R. L., Minshall, G. W., Cummins, K. W., Sedell, J. R., and Cushing, C. E.: The river continuum concept, Can. J. Fish. Aquat. Sci., 37, 130-137, 1980.
Wagner, S., Jaffe , R., Cawley, K., Dittmar, T., and Stubbins, A.: Associations Between the Molecular and Optical Properties of Dissolved Organic Matter in the Florida Everglades, a Model Coastal Wetland System, Front. Chem., 3, doi:10.3389/fchem.2015.00066, 2015.
Walker, S. A., Amon, R. M., and Stedmon, C. A.: Variations in highlatitude riverine fluorescent dissolved organic matter: A comparison of large Arctic rivers, J. Geophys. Res-Biogeo., 118, 1689-1702, doi:10.1002/2013JG002320, 2013.
Ward, N. D., Keil, R. G., Medeiros, P. M., Brito, D. C., Cunha, A. C., Dittmar, T., Yager, P. L., Krusche, A. V., and Richey, J. E.: Degradation of terrestrially derived macromolecules in the Amazon River, Nat. Geosci., 6, 530-533, doi:10.1038/ngeo1817, 2013.
Weishaar, J. L., Aiken, G. R., Bergamaschi, B. A., Fram, M. S., Fujii, R., and Mopper, K.: Evaluation of specific ultraviolet absorbance as an indicator of the chemical composition and reactivity of dissolved organic carbon, Environ. Sci. Technol., 37, 4702-4708, doi:10.1021/es030360x, 2003.
Weyhenmeyer, G. A., Froberg, M., Karltun, E., Khalili, M., Kothawala, D., Temnerud, J., and Tranvik, L. J.: Selective decay of terrestrial organic carbon during transport from land to sea, Glob. Change Biol., 18, 349-355, doi:10.1111/j.1365-2486.2011.02544.x, 2012.
Yamashita, Y., Scinto, L. J., Maie, N., and Jaffe, R.: Dissolved organic matter characteristics across a subtropical wetlands landscape: application of optical properties in the assessment of environmental dynamics, Ecosystems, 13, 1006-1019, doi:10.1007/s10021-010-9370-1, 2010.
Zepp, R. G., Sheldon, W. M., and Moran, M. A.: Dissolved organic fluorophores in southeastern US coastal waters: correction method for eliminating Rayleigh and Raman scattering peaks in excitation-emission matrices, Mar. Chem., 89, 15-36, doi:10.1016/j.marchem.2004.02.006, 2004.
Zurbrugg, R., Suter, S., Lehmann, M. F., Wehrli, B., and Senn, D. B.: Organic carbon and nitrogen export from a tropical dam-impacted floodplain system, Biogeosciences, 10, 23-38, doi:10.5194/bg-10-23-2013, 2013.
