title: Ecology and abundance of oligochaetes as indicators of organic pollution in an urban stream in southern Nigeria.
abstract: A study of the aquatic oligochaetes of an organically polluted segment of an urban stream in Southern Nigeria was carried out to assess the ecological impact of abattoir effluent. Three stations 1, 2 and 3 were selected from upstream of the site receiving abattoir effluent, the impacted site and its down stream, respectively. Among the water quality variables, conductivity, dissolved oxygen, BODs, Nitrate-nitrogen, Phosphate-phosphorus and water hardness were significantly different (p < 0.05) among the stations. Orthogonal comparison using Duncan's multiple range test showed that station 2 (the impacted site) was the cause of the difference. A total of 14 species of oligochaetes were identified with 13 (92.8%) occurring in the impacted station. Tubifex, Dero limnosa and Nais communis were the dominant taxa, less frequent were Stylaria, Aelosoma and Lumbriculus variegatus (Muller). Pistina and Chaetogaster species were sporadically present. The density of the different taxonomic groups differed among the stations with the impacted station accounting for the greatest abundance and diversity of the organisms. The organic wastes from the abattoir not only altered the water chemistry but also stimulated the abundance of oligochaete worms.
authors.affiliation: Department of Zoology, Delta State University, P.M.B. 1, Abraka, Nigeria.
authors.forename: Francis O
authors.initials: FO
authors.lastname: Arimoro
authors.forename: Robert B
authors.initials: RB
authors.lastname: Ikomi
authors.forename: Chukwujindu M A
authors.initials: CM
authors.lastname: Iwegbue
mesh_terms: D000818:Animals; D002947:Cities; D009549:Nigeria; D009835:Oligochaeta / Q000502:physiology*; D045483:Rivers / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical