Assessment Of Biological Integrity Using Physico-chemical Parameters And Macroinvertebrate Community Index Along Sebeta River Ethiopia

The level of water pollution and ecological disturbance of Sebeta River was evaluated usingrnsome important physico-chemical and biological parameters. The Physico-chemicalrnparameters were: flow velocity (m/s), dissolved oxygen (DO) (mg/L), pH, temperature (0c),rnelectrical conductivity (EC) (μs/cm), nitrate-nitrogen (mg/L) and phosphate (mg/L). The meanrnflow velocity and nitrate-nitrogen measures showed no significant difference between the studyrnsites of Sebeta River (P > 0.05). DO records of the river at the upstream rural sites abovernSebeta Agro-industry (SR1 and SR2) were significantly higher than the DO records of therndownstream sites (P < 0.001). The mean pH values of SR3 (3.60 ± 0.81) (immediatelyrndownstream from Bale Zaf Alcohol and Liquor Factory and Soap Factory) and SR4 (4.75 ±rn0.88) (downstream of National Alcohol and Liquor Factory and Blue Nile Tannery) werernsignificantly lower than the pH values of the rest of the sample sites (P < 0.001). The meanrntemperature and EC records of SR3 (33.83 ± 1.17 0c, 16050.00 ± 2270.77 μs/cm) and SR4rn(27.63 ± 0.68 0c, 15400.00 ± 316.60 μs/cm) were significantly higher than the respectivernrecords at the rest of the study sites (P < 0.001). Phosphate concentration at SR3 (8.59 ± 1.16rnmg/L) was significantly higher than the phosphate concentrations recorded from the other sitesrn(P < 0.001). Flow velocity and nitrate-nitrogen of Sebeta River were in the natural range,rnexcept for extreme values at sites SR3 and SR4. Habitat integrity assessment was donernaccording to the US Environmental Protection Agency Rapid Bioassessment Protocol. Percentrncomparability of habitat scores classified the upstream reference sites to good, while itrncategorized the entire downstream sites to very poor. The mean chlorophyll ‘a’ measures ofrnupstream reference sites (SR1 and SR2) showed significantly higher values than those of thernimpacted downstream sites (P < 0.001). Macroinvertebrate community index of Sebeta Riverrn(MCISR) was developed using selected metrics. The MCISR score classified both of thernupstream sites (SR1 and SR2) to very good biological integrity, while it classified all therndownsteam sites to very poor biological integrity, but SR8 (further down in Atebela peasantsrnassociation) to poor.

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