A A comparison in Diel Organic Matter Drift in two Great Rift Valley Streams, Kenya
Drift in streams
Riparian plant litter serve as the main energy source for low order streams where opportunities for photosynthesis are limited by the canopy cover shading. Transport, retention and breakdown of this matter is crucial for stream metabolism. Drifting organic matter was collected over a 24 hr period between 7th and 8th February 2012 in the Njoro (disturbed) and 17th to 18th February 2012 in the Ellegirini (less disturbed) streams. Two drift samplers (mesh size 100 µm) were emptied every 15 minutes. It was hypothesized that the quantity of organic matter drifting from both streams is not the same. Significantly, more organic matter (pooled data) drifted in Ellegirini than in the Njoro River (t = 9.200, d.f = 150, p < 0.001). Organic matter that drifted during the day was significantly higher than during the night (t = 2.812, d.f = 70, p < 0.01) in the Njoro River. This was not the case in the Ellegirini River (t = 0.751, d.f = 76 p > 0.05). Leaves dominated other plant categories in both streams. It is concluded that organic matter drift in large quantities in less disturbed than disturbed rivers and as a consequence can support diverse communities. It is advisable to link organic matter drift with benthos in future studies for better understanding of organic matter dynamics in tropical streams.
Key words: day, disturbance, driftnets, night, plant litter, streams