Water quality changes in relation to Diptera community patterns and diversity measured at an organic effluent impacted stream in the Niger Delta,Nigeria

Impact of abattoir effluents (characterized by intestinal and stomach contents of slaughtered animals, ashes from roasted animals and blood stains) on water quality, distribution and abundance of Diptera were investigated in an urban stream, River Orogodo, Southern Nigeria, from July 2003 to June 2004. Water quality changes indicated significant differences (p < 0.05) in conductivity, dissolved oxygen, BOD₅, COD, total hardness, nitrate-nitrogen and phosphate-phosphorus between the three stations sampled. Higher values of these parameters were observed at the impacted station. The abundance and community structure of Diptera patterns, especially Chironomidae, Culicidae and Syrphidae families (all indicative of poor water quality) showed strong evidence of impact from the abattoir effluents. Comparisons of abundance values demonstrated high significance (p < 0.05) between the impacted station and the upstream (station 1) and downstream station (station 3). Shannon index and Berger–Parker dominance were greater at the impacted station (station 2). Analysis of faunal similarities showed that upstream station 1(unpolluted site) was significantly different from stations 2 and 3. The distinct taxa found in station 2 (the impacted station) suggest that the organic input from the abattoir favoured their abundance as most of them were opportunistic species.