Use of macrophytes in the bioassessment of the health of King'wal Wetland, Lake Victoria Basin, Kenya

摘要

King 'wal wetland, at the upper catchment of Lake Victoria, is undergoing anthropogenic disturbances which degrade its health. In this study, the wetland's health was assessed using water quality parameters and wetland macrophytes, sampled monthly at five stations from November 2010 to February 2011, and the health was evaluated using the Plant Index of Biotic Integrity. Mean dissolved oxygen and biological oxygen demand were significantly different among the stations (F = 10.67, p = 0.000 and F = 10.12, p = 0.000, respectively). Correlation matrix in principle component analysis for stations and the two mean measurements were negative in stations 3, 4 and 5 with component 1 at 62.3% variance and component 2 at 33.9% variance, and positive for mean TN and TP in the same stations indicating a nutrient rich environment. Anthropogenic activities including agriculture, livestock grazing, human settlement and urbanization were the main threats to the health of King'wal wetland. The index scores at the three transect delineated areas with minimum disturbance (ST 3) and those that were highly disturbed (ST 5). However, the entire wetland can be classified as being moderate in health. Wise use and regular monitoring of the wetland is recommended to ensure maintenance of its health.