Macroinvertebrates as Indicators of Water Quality in Thomas Dam, Dambatta, Kano State, Nigeria

Abstract

A study on the water quality assessment using benthic macroinvertebrates in Thomas Dam, Dambatta, Kano State was carried out fortnightly for a period of four months (January–April, 2016). Four sampling sites were chosen based on the vegetation pattern and impact of human activities on the dam. Modified Ekman grab sampler was used for benthic macroinvertebrates collection and identified using standard identification keys. Standard methods were used to determine the physicochemical parameters. The mean range of physicochemical parameters studied were: water temperature (19.6±1.12–23.0±1.00 °C), pH (7.6±0.20–8.2±0.25), DO (6.1±2.88–9.4±0.24 mg/L), BOD (3.0±0.30–5.6±0.25 mg/L), TDS (150.6±2.88–183.3±5.77 mg/L), turbidity (18.8±0.80–41.9±0.26 NTU), electrical conductivity (161.3±1.52–195.6±0.57 µS/cm), N03-N (1.2±0.19–3.5±0.20 mg/L), and PO43-P (0.1±0.05–0.3±0.03 mg/L). There was no significant difference between the sampling sites in physicochemical parameters (P<0.05). Nine (9) taxa comprising 33 species belonging to Arthropoda, Annelida, and Mollusca were identified, accounting for 1162 individuals. Increasing dominance of benthic macroinvertebrates followed the order: Mollusca (35%) > Coleoptera (28%) > Diptera (12.7%) > Annelida (11.4%) > Trichoptera (4.96%) > Plecoptera (3.6%) > Ephemeroptera (3%) > Hemiptera (0.85%) > Odonata (0.08%). Correlation analysis between benthic macroinvertebrate distribution and abundance and physicochemical parameters showed a strong positive relationship (P<0.05). Presence of pollution-tolerant macroinvertebrates, notably Chironomus sp. and Tubifex sp., indicates the dam is under pollution stress. Species diversity indices showed a variation in the community structure in the dam, and the implications of this to the biotic status of the dam are discussed.