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Sediment and carbon fluxes along a longitudinal gradient in the lower Tana River (Kenya)
Author(s) -
Tamooh Fredrick,
Meysman Filip J. R.,
Borges Alberto V.,
Marwick Trent R.,
Van Den Meersche Karel,
Dehairs Frank,
Merckx Roel,
Bouillon Steven
Publication year - 2014
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/2013jg002358
Subject(s) - dissolved organic carbon , total organic carbon , environmental science , particulates , hydrology (agriculture) , sediment trap , sediment , seasonality , organic matter , carbon fibers , flux (metallurgy) , environmental chemistry , chemistry , geology , ecology , geomorphology , biology , materials science , geotechnical engineering , organic chemistry , composite number , composite material
We estimated annual fluxes of suspended matter and different carbon (C) pools at three sites along the lower Tana River (Kenya), based on monthly sampling between January 2009 and December 2011. Concentrations of total suspended matter (TSM), particulate organic carbon (POC), dissolved organic carbon (DOC), and dissolved inorganic carbon (DIC) were monitored, as was the stable isotope composition of the carbon pools. Both TSM and POC concentrations showed strong seasonality, varying over several orders of magnitude, while DOC and DIC concentrations showed no seasonal variations. A strong shift in the origin of POC was observed, which was dominated by C3‐derived C during dry conditions (low δ 13 C POC between −28‰ and −25‰), but had significant C4 contributions during high‐flow events (δ 13 C POC up to −19.5‰). Between Garissa and the most downstream sampling point, a clear decrease in suspended matter and organic C fluxes was observed, being most pronounced during high‐discharge conditions: on an annual basis, fluxes of TSM, POC, and DIC decreased by 34% to 65% for the 3 year study period. Our results suggest that floodplains along the lower Tana River could play an important role in regulating the transport of suspended matter and organic C. A comparison of current flux estimates with data collected prior to the construction of several hydropower dams reveals that the sediment loading is reduced during low discharge conditions.