Macroinvertebrates' community structure in Rivers Kipkaren and Sosiani, River Nzoia basin, Kenya

Abstract

Benthic macroinvertebrates from Rivers Kipkaren and Sosiani in the upper reaches of River Nzoia basin, Kenya, were sampled semi-quantitatively monthly from December 2006 to May 2007 using a 0.5 mm mesh size scoop net in the riffles, pools and runs. Seven sampling sites were selected on the areas of the rivers along a longitudinal gradient in relation to anthropogenic impact. Physico-chemical parameters were measured in situ, while specific chemical parameters were determined calometrically in the laboratory using standard methods. Habitat and land use characteristics were also recorded. A total of 1499 macroinvertebrates belonging to 13 orders, 28 families and 31 genera were collected. The orders Ephemeroptera, Hemiptera and Coleoptera were taxonomically richest. Overall, a total of 31 genera for River Kipkaren dominated by the EPT and 19 macroinvertebrate genera for the lower River Sosiani dominated by dipterans were recorded. Conductivity, oxygen and total nitrogen varied significantly (p < 0.05) between sampled sites, but not temporally. The results of redundancy analysis using 9 dominant macroinvertebrate genera revealed a distinction between impacted and the less impacted sites and the physico-chemical parameters associated with this distinction.   Key words: Physico-chemical parameters, impacted sites, less impacted sites.