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Hydrologic control of carbon cycling and aged carbon discharge in the Congo River basin

Nature Geoscience volume 9, pages 687–690 (2016)Cite this article

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Abstract

The age of organic material discharged by rivers provides information about its sources and carbon cycling processes within watersheds. Although elevated ages in fluvially transported organic matter are usually explained by erosion of soils and sedimentary deposits1,2, it is commonly assumed that mainly young organic material is discharged from flat tropical watersheds due to their extensive plant cover and rapid carbon turnover3,4,5,6,7. Here we present compound-specific radiocarbon data of terrigenous organic fractions from a sedimentary archive offshore the Congo River, in conjunction with molecular markers for methane-producing land cover reflecting wetland extent. We find that the Congo River has been discharging aged organic matter for several thousand years, with apparently increasing ages from the mid- to the Late Holocene. This suggests that aged organic matter in modern samples is concealed by radiocarbon from atmospheric nuclear weapons testing. By comparison to indicators for past rainfall changes we detect a systematic control of organic matter sequestration and release by continental hydrology, mediating temporary carbon storage in wetlands. As aridification also leads to exposure and rapid remineralization of large amounts of previously stored labile organic matter, we infer that this process may cause a profound direct climate feedback that is at present underestimated in carbon cycle assessments.

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Figure 1: The Congo River basin in central Africa.
Figure 2: OM ages offshore the Congo River and central African environmental changes.
Figure 3: Correlation of age variations between different OM fractions.
Figure 4: Relation between rainfall intensity and OM ages.

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References

  1. Raymond, P. A. & Bauer, J. E. Riverine export of aged terrestrial organic matter to the North Atlantic Ocean. Nature 409, 497–500 (2001).

    Article  Google Scholar 

  2. Hilton, R. G. et al. Climatic and geomorphic controls on the erosion of terrestrial biomass from subtropical mountain forest. Glob. Biogeochem. Cycles 26, GB3014 (2012).

    Article  Google Scholar 

  3. Hedges, J. I. et al. Organic carbon-14 in the Amazon River system. Science 231, 1129–1131 (1986).

    Article  Google Scholar 

  4. Martin, E. E. et al. Age of riverine carbon suggests rapid export of terrestrial primary production in tropics. Geophys. Res. Lett. 40, 5687–5691 (2013).

    Article  Google Scholar 

  5. Spencer, R. G. M. et al. An initial investigation into the organic matter biogeochemistry of the Congo River. Geochim. Cosmochim. Acta 84, 614–627 (2012).

    Article  Google Scholar 

  6. Galy, V. & Eglinton, T. Protracted storage of biospheric carbon in the Ganges-Brahmaputra basin. Nat. Geosci. 4, 843–847 (2011).

    Article  Google Scholar 

  7. Marwick, T. R. et al. The age of river-transported carbon: a global perspective. Glob. Biogeochem. Cycles 29, GB004911 (2015).

    Article  Google Scholar 

  8. Carvalhais, N. et al. Global covariation of carbon turnover times with climate in terrestrial ecosystems. Nature 514, 213–217 (2014).

    Article  Google Scholar 

  9. Huang, T. H., Fu, Y. H., Pan, P. Y. & Chen, C. T. A. Fluvial carbon fluxes in tropical rivers. Curr. Opin. Environ. Sustain. 4, 162–169 (2012).

    Article  Google Scholar 

  10. Schluenz, B. & Schneider, R. R. Transport of terrestrial organic carbon to the oceans by rivers: re-estimating flux- and burial rates. Int. J. Earth Sci. 88, 599–606 (2000).

    Article  Google Scholar 

  11. Blair, N. E., Leithold, E. L. & Aller, R. C. From bedrock to burial: the evolution of particulate organic carbon across coupled watershed-continental margin systems. Mar. Chem. 92, 141–156 (2004).

    Article  Google Scholar 

  12. Kusch, S., Rethemeyer, J., Schefuß, E. & Mollenhauer, G. Controls on the age of vascular plant biomarkers in Black Sea sediments. Geochim. Cosmochim. Acta 74, 7031–7047 (2010).

    Article  Google Scholar 

  13. Drenzek, N. J. et al. A new look at old carbon in active margin sediments. Geology 37, 239–242 (2009).

    Article  Google Scholar 

  14. Runge, J. in Large Rivers: Geomorphology and Management (ed. Gupta, A.) 293–309 (Wiley, 2007).

    Book  Google Scholar 

  15. Coynel, A., Seyler, P., Etcheber, H., Meybeck, M. & Orange, D. Spatial and seasonal dynamics of total suspended sediment and organic carbon species in the Congo River. Glob. Biogeochem. Cycles 19, GB4019 (2005).

    Article  Google Scholar 

  16. Laraque, A., Bricquet, J. P., Pandi, A. & Olivry, J. C. A review of material transport by the Congo River and its tributaries. Hydrol. Process. 23, 3216–3224 (2009).

    Article  Google Scholar 

  17. Huang, Y., Li, B., Bryant, C., Bol, R. & Eglinton, G. Radiocarbon dating of aliphatic hydrocarbons: a new approach for dating passive-fraction carbon in soil horizons. Soil Sci. Soc. Am. J. 63, 1181–1187 (1999).

    Article  Google Scholar 

  18. Weijers, J. W. H., Schouten, S., Schefuss, E., Schneider, R. R. & Sinninghe Damsté, J. S. Disentangling marine, soil and plant organic carbon contributions to continental margin sediments: a multi-proxy approach in a 20,000 year sediment record from the Congo deep-sea fan. Geochim. Cosmochim. Acta 73, 119–132 (2009).

    Article  Google Scholar 

  19. Weijers, J. W. H., Schefuss, E., Schouten, S. & Sinninghe Damsté, J. S. Coupled thermal and hydrological evolution of tropical Africa over the last deglaciation. Science 315, 1701–1704 (2007).

    Article  Google Scholar 

  20. Davidson, E. A. & Janssens, I. A. Temperature sensitivity of soil carbon decomposition and feedbacks to climate change. Nature 440, 165–173 (2006).

    Article  Google Scholar 

  21. Schefuß, E., Schouten, S. & Schneider, R. R. Climatic controls of Central African hydrology during the last 20,000 years. Nature 437, 1003–1006 (2005).

    Article  Google Scholar 

  22. Spencer-Jones, C. L. et al. Bacteriohopanepolyols in tropical soils and sediments from the Congo River catchment area. Org. Geochem. 89–90, 1–13 (2015).

    Article  Google Scholar 

  23. Talbot, H. M. et al. Variability in aerobic methane oxidation over the past 1.2 Myrs recorded in microbial biomarker signatures from Congo fan sediments. Geochim. Cosmochim. Acta 133, 387–401 (2014).

    Article  Google Scholar 

  24. Bwangoy, J. R. B., Hansen, M. C., Roy, D. P., De Grandi, G. & 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).

    Article  Google Scholar 

  25. Mitsch, W. J. et al. Wetlands, carbon, and climate change. Landsc. Ecol. 28, 583–597 (2013).

    Article  Google Scholar 

  26. Kayranli, B., Scholz, M., Mustafa, A. & Hedmark, A. Carbon storage and fluxes within freshwater wetlands: a critical review. Wetlands 30, 111–124 (2010).

    Article  Google Scholar 

  27. Keddy, P. A. et al. Wet and wonderful: the World’s largest wetlands are conservation priorities. Bioscience 59, 39–51 (2009).

    Article  Google Scholar 

  28. Joosten, H. & Tapio-Biström, M.-L. Mitigation of Climate Change in Agriculture Vol. 5 (Food and Agriculture Organization of the United Nations/Wetlands International, 2012).

    Google Scholar 

  29. Borges, A. V. et al. Globally significant greenhouse-gas emissions from African inland waters. Nat. Geosci. 8, 637–642 (2015).

    Article  Google Scholar 

  30. Arneth, A. et al. Terrestrial biogeochemical feedbacks in the climate system. Nat. Geosci. 3, 525–532 (2010).

    Article  Google Scholar 

  31. Nadeau, M.-J. et al. Sample throughput and data quality at the Leibniz-Labor AMS facility. Radiocarbon 40, 239–245 (1998).

    Article  Google Scholar 

  32. Reimer, P. J. et al. INTCAL13 and MARINE13 radiocarbon age calibration curves 0–50,000 years cal BP. Radiocarbon 55, 1869–1887 (2013).

    Article  Google Scholar 

  33. Santos, G. M., Southon, J. R., Griffin, S., Beaupre, S. R. & Druffel, E. R. M. Ultra small-mass AMS C-14 sample preparation and analyses at KCCAMS/UCI Facility. Nucl. Instrum. Methods Phys. Res. B 259, 293–302 (2007).

    Article  Google Scholar 

  34. Eglinton, T. I., Aluwihare, L. I., Bauer, J. E., Druffel, E. R. M. & McNichol, A. P. Gas chromatographic isolation of individual compounds from complex matrices for radiocarbon dating. Anal. Chem. 68, 904–912 (1996).

    Article  Google Scholar 

  35. Stuiver, M. & Polach, H. A. Discussion: reporting of 14C data. Radiocarbon 19, 355–363 (1977).

    Article  Google Scholar 

  36. Hogg, A. G. et al. SHCAL13 Southern Hemisphere calibration, 0–50,000 years cal BP. Radiocarbon 55, 1889–1903 (2013).

    Article  Google Scholar 

  37. Levin, I., Kromer, B. & Hammer, S. Atmospheric Delta (CO2)-C-14 trend in Western European background air from 2000 to 2012. Tellus B 65, 20092 (2013).

    Article  Google Scholar 

  38. Eglinton, G. & Hamilton, R. J. Leaf epicuticular waxes. Science 156, 1322–1335 (1967).

    Article  Google Scholar 

  39. Peters, K. E. & Moldowan, J. M. The Biomarker Guide: Interpreting Molecular Fossils in Petroleum and Ancient Sediments (Prentice-Hall, 1993).

    Google Scholar 

  40. van Winden, J. F. et al. Bacteriohopanepolyol signatures as markers for methanotrophic bacteria in peat moss. Geochim. Cosmochim. Acta 77, 52–61 (2012).

    Article  Google Scholar 

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Acknowledgements

We thank J. M. Hayes, G. Mollenhauer, T. Goldhammer, M. Zabel, T. Wagner and M. Schulz for discussions. M. Luttmann, H. Buschhoff, D. Montluçon, F. Sidgwick, P. Green and S. Sylva are thanked for analytical support. We thank the staff at all involved radiocarbon dating facilities for their invaluable efforts. This study was supported by the Deutsche Forschungsgemeinschaft (grants SCHN 621/3-3, RU 458/29-3, GR 1845/2-3, SCHE 903/1), the US National Science Foundation (grant OCE-0137005), a Starting Grant from the European Research Council (ERC) awarded to H.M.T. for project AMOPROX (no. 258734) and grants ICM-NC120066 and FONDECYT1140536 to R.D.P.-H. This work was supported by the DFG Research Center/Cluster of Excellence ‘The Ocean in the Earth System’ at MARUM—Center for Marine Environmental Sciences, University of Bremen.

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Author notes

  1. Charlotte L. Spencer-Jones, Pieter M. Grootes & Ralph R. Schneider

    Present address: Present addresses: Department of Geography, University of Durham, Durham DH1 3LE, UK (C.L.S.-J.); Institute for Ecosystem Research, Christian-Albrechts-University Kiel, 24118 Kiel, Germany (P.M.G., R.R.S.).,

Authors and Affiliations

  1. MARUM—Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany

    Enno Schefuß

  2. Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA

    Enno Schefuß & Timothy I. Eglinton

  3. Department of Geological Sciences, ETH Zürich, 8092 Zürich, Switzerland

    Timothy I. Eglinton

  4. School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK

    Charlotte L. Spencer-Jones & Helen M. Talbot

  5. Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University of Oldenburg, 26111 Oldenburg, Germany

    Jürgen Rullkötter

  6. GAIA-Antártica, Center for Climate and Resilience Research (CR)2, Universidad de Magallanes, 6210427 Punta Arenas, Chile

    Ricardo De Pol-Holz

  7. Leibniz-Laboratory for Radiometric Dating and Stable Isotope Research Kiel, 24105 Kiel, Germany

    Pieter M. Grootes & Ralph R. Schneider

  8. Institute for Geosciences, Christian-Albrechts-University Kiel, 24118 Kiel, Germany

    Ralph R. Schneider

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Contributions

E.S., T.I.E., J.R., P.M.G. and R.R.S. designed the study; analytical work was performed by E.S., C.L.S.-J., H.M.T., J.R., P.M.G. and R.D.P.-H.; E.S. wrote the manuscript, which was approved by all co-authors.

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Correspondence to Enno Schefuß.

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Schefuß, E., Eglinton, T., Spencer-Jones, C. et al. Hydrologic control of carbon cycling and aged carbon discharge in the Congo River basin. Nature Geosci 9, 687–690 (2016). https://doi.org/10.1038/ngeo2778

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