Community structure and diversity of macrobenthic invertebrates in relation to some water quality parameters in a municipal river in southern Nigeria

Abstract

Macrobenthic invertebrates’ community structure and diversity in relation to some water quality parameters of Owan River; Edo State, was investigated from March 2011 to August, 2011. The study was aimed to determine the water-quality and their relationship with the community structure and diversity of macro-invertebrates in the river. Two sampling stations were selected along the river course (Ogute; Station 1 and Evbiamen; Station 2). Quantitative physico-chemical parameters and macro-invertebrates were collected monthly at the two stations. The range of the physico-chemical parameters obtained were Temperature (23.2-26.5^oC), Depth (0.55-2.05 m), flow velocity (0.05-0.48 m/s), conductivity (25.42- 30.94 μS/cm), pH (6.3-7.8), DO (5.2-7.8 mg/l), BOD (1.78-2.4 mg/l), phosphate (0.03-0.58 mg/l) and sulphate (7.8-9.4 mg/l). Analysis of variance (ANOVA) revealed that there were significant difference (p<0.05) in conductivity, temperature, pH, phosphate, BOD, depth and flow velocity between the sampled stations and months, while DO showed significant difference (p<0.05) in the sampled months but not significant (p>0.05) in the sampled station. Sulphate showed no significant difference in the sampled months (p>0.05) but showed significant difference in the sampled stations (p<0.05). A total of 26 taxa of 591 individual were collected. The most abundant taxon was Mollusca (180). The highest number of macroinvertebrates was recorded in Station 2. The Canonical Correspondence Analysis showed a fairly good relationship between some macrobenthic invertebrates’ species distribution and some measured environmental variables. Water depth, pH and DO were negatively correlated with sulphate and flow velocity. Melanoides moerchi was slightly affected positively by phosphate while Stenophylax sp., Potadoma moerchi were fairly associated with increased conductivity. Analysis of species diversity revealed that the highest number of taxa richness was recorded in Station 2, while Station 1 had the highest species diversity. Simpson dominance (D) was higher in Station 2 compared to Station 1. From the physico-chemical parameters and macrobenthic structure-showed that the river may be subjected to perturbation in the nearest future as a result of the various level of anthropogenic activities carried on in the river.

Keywords: macrobenthic invertebrates, mollusca, Owan River, diversity and southern Nigeria.