Macroinvertebrate Index of Biotic Integrity for Assessing the Water Quality of Rivers Kipkaren and Sosiani, Nzoia River Basin, Kenya.
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AuthorAura, Christopher Mulanda
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AbstractGlobally, IBI is being applied as an integrity tool in monitoring and bioassessment of aquatic ecosystems such as rivers. The study set out to investigate the possibility of establishing an Index of Biotic Integrity (IBI) using macroinvertebrates to asses the water quality with special reference to nutrient levels of Rivers Kipkaren and Sosiani in the upper reaches of River Nzoia Basin, Kenya. Physical water quality parameters like pH, conductivity, temperature, water velocity and discharge were measured while chemical parameters such as DO, TP and TN were determined calorimetrically in the laboratory using standard methods. Habitat and land use characteristics were also recorded. Triplicate macroinvertebrate samples were collected semi-quantitatively on a monthly basis from December 2006 to May 2007 using a 0.5 mm mesh size scoop net in the riffles, pools and runs. Macroinvertebrates were analyzed for abundance and diversity and related to the nutrients (TP and TN) using the Spearman’s correlation analysis. Statistical tests of Mann-Whitney U and Kolmogorov-Smirnov tests were used for pair wise comparison in all the stations and provided 9 macroinvertebrate metrics that contributed significantly (p<0.05) to the final IBI. SPSS for Windows version 10.0 and Microsoft Excel computer packages were used for statistical analyses. A total of 31 macroinvertebrate genera for River Kipkaren dominated by the EPT and 19 macroinvertebrate genera for the lower River Sosiani dominated by dipterans were recorded. Significant differences in the mean abundance (F= 16.371; df = 6; p = 0.000) and diversity (H=7; df=7; p=0.0032) between the stations were found that indicated differences in water quality. A significant positive correlation for TN and TP and macroinvertebrates was obtained (p=0.00; r =0.39). In the final IBI, River Kipkaren stations had better water quality with IBI ranging from 27 to 39 points, while River Sosiani stations fell in classes of fair to poor water quality and IBI ranging from 19 to 22 points out of the total 45 points due to variations in anthropogenic impacts. The study recommends the use of IBI in biomonitoring and bioassessment of rivers to improve the river health and thus biotic integrity because the IBI delineates impacted from less impacted sites along the rivers. An alternative preliminary IBI using fish and algae assemblages should also be explored for comparison in the Nzoia River Basin.
Publisher or UniversityMoi University