Physico-Chemical and Entomofauna Biodiversity Assessment of Pollution Status of Taabaa Streams, Nigeria

Abstract

Taabaa streams situated at Taabaa-Okwale and East-West roads, Taabaa were investigated using physico-chemical and entomofauna biodiversity indicators to ascertain their pollution status, following series of human activities; bathing/laundry services, cars/motorcycles washing, run-offs from agricultural farms that occur at the streams. The discharge from the run-offs and other sources into the streams may cause increase in the hydro-carbon concentration and phosphates of the water bodies and consequently changes the pH, available dissolved oxygen, and biodiversity composition of the streams, making it unsuitable for its inhabitants and humans that use the water for drinking. This study was conducted to determine the physico-chemical concentrations and entomofauna diversity of the streams. The pH quality meter was used in-situ to obtain readings of pH and dissolved oxygen values. Water samples used for the analysis of chemical variables were collected from the surface water using 250 ml plastic bottles, and taken to the Laboratory where they were measured spectrophotometrically. A rectangular frame dipnet and a kicknet (500 um mesh size) was used to collect insect samples randomly and taken to the Laboratory for sorting and identification. The results indicated a low pH, and available dissolved oxygen of 6.4 and 3.7 mg/l at the station (Taabaa-Okwale Rd) of the stream. It also shows an increase in the concentrations of phosphates (5.8 mg/l) and Total Petroleum Hydrocarbon (3.47 mg/l) which were higher than WHO permissible limits. The entomofauna indicators comprising species richness and abundance, species sensitivity, and species dominance results showed that station 1 recorded 90 and station 2 (East-West Rd) 149 individual insects. The abundance of Hemiptera and Diptera were higher at station 1 and species that belong to Ephemeroptera, Plecoptera and Trichoptera (EPT) were sensitive to the contaminants and were absent at station 1 but occurred at station 2. The bioindicator species encountered at station 1 were Cybister sp., Gyrinus sp., Gerris sp., Corixa sp., and Chironomus sp. and that of station 2 were in addition to EPT species; Pelocoris sp. and Dytiscus sp. Hemiptera was the dominant insect order representing 19.66% and Chironomus sp. the dominant single species collected during the study. The results indicates that the pollution status of station 1 was relatively higher