Terrestrial and fluvial carbon fluxes in a tropical watershed: Nyong basin, Cameroon

• Published in: Chemical geology Vol. 265; no. 3; pp. 563 - 572
• Main Authors: Brunet, F., Dubois, K., Veizer, J., Nkoue Ndondo, G.R., Ndam Ngoupayou, J.R., Boeglin, J.L., Probst, J.L.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30.07.2009; Elsevier
• Subjects: Atmospheric CO 2; Atmospherics; Basins; Biochemistry; Biochemistry, Molecular Biology; Biogenic CO 2; Cameroons; Carbon; Carbon cycle; Carbon isotopes; Dissolution; Dissolved inorganic carbon; Dissolved organic carbon; Earth Sciences; Fluxes; Freshwater; Geochemistry; International trade; Life Sciences; Rivers; Sciences of the Universe; Watersheds; Carbon cycle; Dissolved organic carbon; Biogenic CO 2; Dissolved inorganic carbon; Atmospheric CO 2; Carbon isotopes; Biogenic CO2; Carbon cycle -Dissolved organic carbon; Atmospheric CO2
• ISSN: 0009-2541; 1872-6836
• DOI: 10.1016/j.chemgeo.2009.05.020

The Nyong watershed, with an area of 27 800 km 2 and a mean annual discharge of 390 m 3 s − 1 , is the second largest river in Cameroon. The Nyong watershed serves as an outstanding study area for the examination of carbon fluxes in humid tropical environments because of its limited anthropogenic impact and homogeneous silicate bedrock. Between April 2005 and April 2007, we sampled water at seven stations, from the small watershed of the Mengong (0.6 km 2) to the Nyong at Edea (24 500 km 2), and monitored temperature, pH, dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) contents, as well as the isotopic composition of DIC ( δ 13C DIC) and DOC ( δ 13C DOC). We estimated terrestrial net ecosystem productivity in the Nyong River watershed and measured fluvial fluxes of carbon to the ocean and the atmosphere. The Nyong River basin sequesters significant amounts of carbon on an annual basis: ~ 7 920 000 t C year − 1 (300 g C m − 2 year − 1 ). The combined dissolved organic, dissolved inorganic and atmospheric fluxes of carbon from the Nyong River only export 3% of this flux from the basin on an annual basis. This includes a minimum CO 2 outgassing of 1487 g C m − 2 year − 1 , comparable to 115% of the annual flux of DOC and four times greater than the flux of DIC.