MACROPHYTE BASED INDEX OF BIOTIC INTEGRITY FOR MONITORING ECOLOGICAL INTEGRITY OF CHEPKOILEL RIVER SWAMP, KENYA

Abstract

The study set out to investigate the uses of macrophytes within Chepkoilel river swamp, the impact of those uses on macrophyte community structure and to develop an index for monitoring the ecological integrity of the swamp. Macrophytes were sampled at seven stations along Chepkoilel river swamp one of which became the reference station. Stations were chosen to correspond to different human activities and intensity of human presence Sampling was done at each station for six months. Selected physico-chemical parameters of water were measured at each sampling site. Sampled macrophytes were identified, and taxon diversity, abundance, evenness and non-taxonomic attributes estimated for each station. Composition and distribution results were used to develop a Macrophyte Index of Biotic Integrity that was used for bioassessment of ecological integrity of the swamp. Ten metrics were tested using box-and-whisker plots to determine their variability across a gradient of human disturbance. The riparian community was found to have diverse uses for macrophytes from this swamp with animal grazing, fuelwood collection, wild fruits, and medicinal uses showing high respondent proportion on frequency of use and use preference. Results showed significant (p<0.05) spatial variation in macrophyte community attributes and water quality parameters. The macrophyte attributes further showed significant relationships with water quality parameters. Stations with high human disturbance recorded low abundance and diversity compared to those with low human disturbance. Nine metrics met the test criteria and were used to develop Index of Biotic Integrity development along the swamp. These were total abundance, diversity index, evenness index, vascular plant diversity, non-vascular plant diversity, grasses, sedges, true aquatic plants, and plants with persistent litter. Station 1 obtained a total macrophyte index of Biotic Integrity score of 37 while station 3 obtained a total score of 11. This result indicated that more disturbed stations got low IBI scores compared to the less disturbed ones. Conclusions from the study showed that human disturbance influenced macrophyte composition and abundance along Chepkoilel river swamp consequently influencing the ecological integrity of the swamp. The macrophytes in the swamp can be considered to be reliable indicators of disturbance and the IBI developed should therefore be used to constantly monitor the ecological integrity of the swamp.