ASLO 2011 Aquatic Sciences Meeting location:San Juan, Puerto Rico date:13-18 February 2011
Few studies have quantified carbon fluxes in African tropical rivers. We report the altitudinal and seasonal patterns in carbon pools and their stable isotope composition from the River Basin (Kenya). Data from February 2008 (end of dry season), September-November 2009 (short rains), and June-July 2010 (end of long rains) are
presented. Seasonal data from January 2009-March 2010 are also presented. A consistent downstream increase in TSM was observed during all three sampling campaigns. TSM values were similar for 2008 and 2010 datasets (p>0.05), but significantly higher during the short rains in 2009. δ13C-POC increased downstream (p<0.01), and were
predominantly of terrestrial origin as reflected by generally high POC/Chl a ratios. TSM and %POC followed the classical inverse relationship for all years sampled. TSM
and POC were highly episodic and highest in periods with high discharge. Seasonal patterns in δ13C-POC signatures coincided closely with δ13C increasing markedly during periods of high discharge and decreasing towards predominantly C3 signatures toward the end of dry periods. This suggests high sediment mobilization during rains
occurs mostly in areas with significant grassland cover (C4).