Distribution, origin and cycling of carbon in the Tana River (Kenya): a dry season basin-scale survey from headwaters to the delta

Abstract. The Tana River basin (TRB) is the largest in Kenya (~120 000 km2). We conducted a survey during the dry season throughout the TRB, analyzing a broad suite of biogeochemical parameters. Biogeochemical signatures in headwater streams were highly variable. Along the middle and lower river course, total suspended matter (TSM) concentrations increased more than 30-fold despite the absence of tributary inputs, indicating important resuspension events of internally stored sediment. These resuspended sediment inputs were characterized by a lower and 14C-depleted OC content, suggesting selective degradation of more recent material during sediment retention. Masinga Dam (a large reservoir on the upper river) induced a strong nutrient retention (~50% for inorganic N, ~72% for inorganic phosphate, and ~40% for dissolved silicate). Moreover, while DOC pools and δ13C signatures were similar above, in and below the reservoir, the POC pool in Masinga surface waters was dominated by 13C-depleted phytoplankton, which contributed to the riverine POC pool immediately below the dam, but rapidly disappeared further downstream, suggesting rapid remineralization of this labile C pool in the river system. Despite the generally high turbidity, the combination of relatively high oxygen saturation levels, low δ18O signatures of dissolved O2 (all <+24.2‰), and the relatively low pCO2 values suggest that in-stream primary production was significant, even though pigment data suggest that phytoplankton makes only a minor contribution to the total POC pool in the Tana River.

[1]  F. Guérin,et al.  A multi‐tracers analysis of sources and transfers of particulate organic matter in a tropical reservoir (Petit Saut, French Guiana) , 2009 .

[2]  R. Alexander,et al.  The regional and global significance of nitrogen removal in lakes and reservoirs , 2009 .

[3]  K. Hughen,et al.  A new look at old carbon in active margin sediments , 2009 .

[4]  Jack J. Middelburg,et al.  Carbon biogeochemistry of the Betsiboka estuary (north-western Madagascar) , 2008 .

[5]  Robert G. Hilton,et al.  Tropical-cyclone-driven erosion of the terrestrial biosphere from mountains , 2008 .

[6]  Mark S. Johnson,et al.  CO2 efflux from Amazonian headwater streams represents a significant fate for deep soil respiration , 2008 .

[7]  C. Kendall,et al.  Carbon isotope fractionation of dissolved inorganic carbon (DIC) due to outgassing of carbon dioxide from a headwater stream , 2008 .

[8]  A. Galy,et al.  Himalaya--Carbon Sink or Source? , 2008, Science.

[9]  C. France‐Lanord,et al.  Loading and fate of particulate organic carbon from the Himalaya to the Ganga–Brahmaputra delta , 2008 .

[10]  R. Naiman,et al.  Andean Influences on the Biogeochemistry and Ecology of the Amazon River , 2008 .

[11]  L. Derry,et al.  Degassing of metamorphic carbon dioxide from the Nepal Himalaya , 2008 .

[12]  W. Dietrich,et al.  Biogeochemical characterization of carbon sources in the Strickland and Fly rivers, Papua New Guinea , 2008 .

[13]  M. Stieglitz,et al.  Lability of DOC transported by Alaskan rivers to the Arctic Ocean , 2008 .

[14]  G. Gleixner,et al.  Soil organic matter in soil depth profiles: Distinct carbon preferences of microbial groups during carbon transformation , 2008 .

[15]  A. Townsend‐Small,et al.  Suspended sediments and organic matter in mountain headwaters of the Amazon River: Results from a 1-year time series study in the central Peruvian Andes , 2008 .

[16]  N. Oh,et al.  Anthropogenically enhanced fluxes of water and carbon from the Mississippi River , 2008, Nature.

[17]  Aaron I. Packman,et al.  Biophysical controls on organic carbon fluxes in fluvial networks , 2008 .

[18]  M. Pace,et al.  Relative independence of organic carbon transport and processing in a large temperate river: The Hudson River as both pipe and reactor , 2008 .

[19]  C. Masiello.  Carbon cycle: Quick burial at sea , 2007, Nature.

[20]  Christopher L. Osburn,et al.  The use of wet chemical oxidation with high‐amplification isotope ratio mass spectrometry (WCO‐IRMS) to measure stable isotope values of dissolved organic carbon in seawater , 2007 .

[21]  F. Guérin,et al.  Significance of pelagic aerobic methane oxidation in the methane and carbon budget of a tropical reservoir , 2007 .

[22]  Peter M. J. Herman,et al.  Organic matter processing in tidal estuaries , 2007 .

[23]  J. Böhlke,et al.  The oxygen‐18 isotope approach for measuring aquatic metabolism in high productivity waters , 2007 .

[24]  S. Bouillon,et al.  Determination of delta18O of water and delta13C of dissolved inorganic carbon using a simple modification of an elemental analyser-isotope ratio mass spectrometer: an evaluation. , 2007, Rapid communications in mass spectrometry : RCM.

[25]  Yohanna Shaghude,et al.  Downstream and Coastal Impacts of Damming and Water Abstraction in Africa , 2007, Environmental management.

[26]  Christopher A Williams,et al.  Africa and the global carbon cycle , 2007, Carbon balance and management.

[27]  P. Quay,et al.  Organic matter in the Peruvian headwaters of the Amazon: Compositional evolution from the Andes to the lowland Amazon mainstem , 2007 .

[28]  J. Deborde,et al.  The dynamics of phosphorus in turbid estuarine systems: Example of the Gironde estuary (France) , 2007 .

[29]  J. Downing,et al.  Plumbing the Global Carbon Cycle: Integrating Inland Waters into the Terrestrial Carbon Budget , 2007, Ecosystems.

[30]  A. Borges,et al.  Biogeochemistry of the Tana estuary and delta (northern Kenya) , 2007 .

[31]  F. Guérin,et al.  Enhanced methane oxidation in an estuarine turbidity maximum , 2007 .

[32]  Sandrine Richard,et al.  Methane and carbon dioxide emissions from tropical reservoirs: Significance of downstream rivers , 2006 .

[33]  G. Gleixner,et al.  Variable use of plant- and soil-derived carbon by microorganisms in agricultural soils , 2006 .

[34]  A. Pierson‐Wickmann,et al.  Fluxes and sources of particulate organic carbon in the Ganga‐Brahmaputra river system , 2006 .

[35]  H. Boschker,et al.  Bacterial carbon sources in coastal sediments: a cross-system analysis based on stable isotope data of biomarkers , 2006 .

[36]  Wilfred M. Wollheim,et al.  Relationship between river size and nutrient removal , 2006 .

[37]  Louis Varfalvy,et al.  Carbon dioxide and methane emissions and the carbon budget of a 10‐year old tropical reservoir (Petit Saut, French Guiana) , 2005 .

[38]  Michel Meybeck,et al.  Spatial and seasonal dynamics of total suspended sediment and organic carbon species in the Congo River , 2005 .

[39]  W. Bond,et al.  Taxonomic, anatomical, and spatio-temporal variations in the stable carbon and nitrogen isotopic compositions of plants from an African savanna , 2005 .

[40]  J. Probst,et al.  δ13C tracing of dissolved inorganic carbon sources in Patagonian rivers (Argentina) , 2005 .

[41]  C. Duarte,et al.  Prevalence of Heterotrophy and Atmospheric CO2 Emissions from Aquatic Ecosystems , 2005, Ecosystems.

[42]  C. Masiello,et al.  Young organic matter as a source of carbon dioxide outgassing from Amazonian rivers , 2005, Nature.

[43]  Jonathan J. Cole,et al.  Temperature independence of carbon dioxide supersaturation in global lakes , 2005 .

[44]  Johnson U. Kitheka,et al.  River discharge, sediment transport and exchange in the Tana Estuary, Kenya , 2005 .

[45]  J. Syvitski,et al.  Impact of Humans on the Flux of Terrestrial Sediment to the Global Coastal Ocean , 2005, Science.

[46]  A. Townsend‐Small,et al.  Contributions of carbon and nitrogen from the Andes Mountains to the Amazon River: Evidence from an elevational gradient of soils, plants, and river material , 2005 .

[47]  A. Borges.  Do we have enough pieces of the jigsaw to integrate CO2 fluxes in the coastal ocean? , 2005 .

[48]  H. Ducklow,et al.  Assessing sources and ages of organic matter supporting river and estuarine bacterial production: A multiple‐isotope (Δ14C, 㬔C, and δ15N) approach , 2004 .

[49]  N. Batjes.  Soil carbon stocks and projected changes according to land use and management: a case study for Kenya , 2004 .

[50]  P. Johnes,et al.  Physico-chemical controls on phosphorus cycling in two lowland streams. Part 2--the sediment phase. , 2004, The Science of the total environment.

[51]  Jean Pierre Henry Balbaud Ometto,et al.  RIVERINE ORGANIC MATTER COMPOSITION AS A FUNCTION OF LAND USE CHANGES, SOUTHWEST AMAZON , 2004 .

[52]  L. Gillson,et al.  Interpretation of soil δ13C as an indicator of vegetation change in African savannas , 2004 .

[53]  C. Vörösmarty,et al.  Anthropogenic sediment retention: major global impact from registered river impoundments , 2003 .

[54]  William H. McDowell,et al.  Biogeochemical Hot Spots and Hot Moments at the Interface of Terrestrial and Aquatic Ecosystems , 2003, Ecosystems.

[55]  Gilles St-Jean,et al.  Automated quantitative and isotopic (13C) analysis of dissolved inorganic carbon and dissolved organic carbon in continuous-flow using a total organic carbon analyser. , 2003, Rapid communications in mass spectrometry : RCM.

[56]  R. Seifert,et al.  Methane distribution in European tidal estuaries , 2002 .

[57]  L. Hess,et al.  Outgassing from Amazonian rivers and wetlands as a large tropical source of atmospheric CO2 , 2002, Nature.

[58]  N. Iversen,et al.  Methane dynamics in a shallow non-tidal estuary (Randers Fjord, Denmark) , 2002 .

[59]  G. Cabeçadas,et al.  Behaviour of Organic Carbon in Nine Contrasting European Estuaries , 2002 .

[60]  A. Borges,et al.  Direct and Indirect pCO2 Measurements in a Wide Range of pCO2 and Salinity Values (The Scheldt Estuary) , 2001 .

[61]  P. Raymond,et al.  Use of 14C and 13C natural abundances for evaluating riverine, estuarine, and coastal DOC and POC sources and cycling: a review and synthesis , 2001 .

[62]  N. Caraco,et al.  Carbon in catchments: connecting terrestrial carbon losses with aquatic metabolism , 2001 .

[63]  C. Humborg,et al.  Hydrological Alterations and Marine Biogeochemistry: A Silicate Issue? , 2000 .

[64]  D. M. Rosenberg,et al.  Reservoir Surfaces as Sources of Greenhouse Gases to the Atmosphere: A Global Estimate , 2000 .

[65]  William H. McDowell,et al.  Soil C:N ratio as a predictor of annual riverine DOC flux at local and global scales , 2000 .

[66]  P. D. de Camargo,et al.  Landcover changes and δ13C composition of riverine particulate organic matter in the piracicaba river basin (southeast region of brazil) , 1999 .

[67]  A. Aucour,et al.  Use of 13C to trace origin and cycling of inorganic carbon in the Rhône river system , 1999 .

[68]  M. Billett,et al.  The relationship between dissolved organic carbon in stream water and soil organic carbon pools at different spatial scales , 1999 .

[69]  W. Dietrich,et al.  The soil production function and landscape equilibrium , 1997, Nature.

[70]  A. Devol,et al.  Isotopic fractionation of oxygen and nitrogen in coastal marine sediments , 1997 .

[71]  P. Quay,et al.  Loss of organic matter from riverine particles in deltas , 1997 .

[72]  Joann Mossa,et al.  Sediment dynamics in the lowermost Mississippi River , 1996 .

[73]  N. Batjes,et al.  Total carbon and nitrogen in the soils of the world , 1996 .

[74]  B. Forsberg,et al.  The 18O:16O of dissolved oxygen in rivers and lakes in the Amazon Basin: Determining the ratio of respiration to photosynthesis rates in freshwaters , 1995 .

[75]  A. Chivas,et al.  Effect of forest and savanna vegetation on the carbon‐isotope composition of sediments from the Sanaga River, Cameroon , 1994 .

[76]  G. Kling,et al.  Carbon Dioxide Supersaturation in the Surface Waters of Lakes , 1994, Science.

[77]  B. Forsberg,et al.  Origins and processing of organic matter in the Amazon River as indicated by carbohydrates and amino acids , 1994 .

[78]  L. Mayer.  SURFACE AREA CONTROL OF ORGANIC CARBON ACCUMULATION IN CONTINENTAL SHELF SEDIMENTS , 1994 .

[79]  M. Scranton,et al.  Fate of methane in the Hudson River and Estuary , 1993 .

[80]  J. Berry,et al.  Photosynthetic Fractionation of the Stable Isotopes of Oxygen and Carbon , 1993, Plant physiology.

[81]  L. E. Fox.  A model for inorganic control of phosphate concentrations in river waters , 1989 .

[82]  M. Lilley,et al.  Methane in surface waters of Oregon estuaries and rivers1 , 1987 .

[83]  S. Wofsy,et al.  The chemical control of soluble phosphorus in the Amazon estuary , 1986 .

[84]  R. H. Meade,et al.  Storage and Remobilization of Suspended Sediment in the Lower Amazon River of Brazil , 1985, Science.

[85]  Dda Piesold,et al.  MASINGA DAM IN KENYA. , 1984 .

[86]  T. Dunne,et al.  Sediment yield and land use in tropical catchments , 1979 .

[87]  P. Giorgio,et al.  Relative independence of dissolved organic carbon transport and processing in a large temperate river: The Hudson River as both pipe and reactor , 2007 .

[88]  A. Klik,et al.  Predictings Sediment Loading into Masinga Reservoir and its Storage Capacity Reduction , 2005 .

[89]  C. Vörösmarty,et al.  Fluvial filtering of land-to-ocean fluxes: from natural Holocene variations to Anthropocene , 2005 .

[90]  D. Orange,et al.  Spatial and seasonal dynamics of total suspended sediment and organic carbon species in the Congo River - art. no. GB4019 , 2005 .

[91]  L. Tieszen,et al.  The distribution of C3 and C4 grasses and carbon isotope discrimination along an altitudinal and moisture gradient in Kenya , 2004, Oecologia.

[92]  K. Mavuti,et al.  Comparative limnology, species diversity and biomass relationship of zooplankton and phytoplankton in five freshwater lakes in Kenya , 2004, Hydrobiologia.

[93]  J. E. Cox,et al.  Stable carbon isotope ratio and composition of microbial fatty acids in tropical soils. , 2003, Journal of environmental quality.

[94]  W. Saenyi.  Temporal and Spatial Sediment Modelling in Masinga Reservoir, Kenya , 2003 .

[95]  John K. Maingi,et al.  Quantifying hydrologic impacts following dam construction along the Tana River, Kenya , 2002 .

[96]  F. Gichuki,et al.  Sediment sources to Masinga dam. , 2000 .

[97]  Jeremy B. Jones,et al.  Influence of drainage basin topography and elevation on carbon dioxide and methane supersaturation of stream water , 1998 .

[98]  W. Ludwig,et al.  River discharges of carbon to the world's oceans: determining local inputs of alkalinity and of dissolved and particulate organic carbon , 1996 .

[99]  R. H. Meade.  Movement and Storage of Sediment in River Systems , 1988 .

[100]  D. Walling.  The sediment yields of African rivers , 1984 .

[101]  M. Stuiver,et al.  Discussion Reporting of 14C Data , 1977, Radiocarbon.