THE IMPACT OF WATER QUALITY DETERIORATION ON MACROINVERTEBRATE COMMUNITIES IN THE LAKE TANA, NORTHWESTERN ETHIOPIA: ANALYSIS USING TOLERANCE LEVEL APPROACH

Abstract

Lake Tana is a biodiversity reservoir and freshwater supplier that contribut significantly to the economy of Ethiopia and downstream recipient countries (Sudan and Egypt). Due to human activities, water quality and biodiversity of the lake was threatened. Some of the most significant contributors to the lake pollution include domestic sewage, agricultural inputs and outputs, industrial inputs and outputs, silt from the agricultural activity, etc in the catchement. To asses the impact of antropogenic activities of Lake Tana, macroinvertabrates were analysed in dry and wet seasons at 11 sampling sites. In the analysis, litratures indicated that the presence of more Odonata, Coleptera and Hemipteran larvae is the indication of water quality deterioration due pollution. From the collected organisms total numbers of tolerant individuals were 303 (48.2 %) and Facultative individuals were 243 (38.7 %) while intolerant individual organisms were 80 (12.7 %). Most of the taxa (48.2 %) had tolerance scores ranging from 7 to 10. In general, all the sampling stations show the degradation of water quality and thus needs for mitigation measures and management options to save Lake Tana.