Document Type: Primary Research paper
Owena reservoir was established for the supply of portable water, fisheries exploitation, irrigation of agricultural lands and hydro-electricity. These activities subject the reservoir to environmental degradation which will reflect on the quality of water, sediment and organisms. This necessitates the study since abundance, diversity, biomass and composition of the benthic invertebrates can be used as indicators of changing environmental conditions. Hence, on monthly basis (February–April, 2013), macro-benthic invertebrates were collected from Owena reservoir using Van veen grab. Also, some physico-chemical parameters were determined. Five species of macro-benthic invertebrates were recorded, which include Chironomus larva (24), Melanoides tuberculata (80), Physa waterlotti (6), Bulinus globussus (12) and Lynmea natalensis (6) belonging to two phyla; Arthropoda and Mollusca. The analysis of the physiochemical parameters showed that a negative relationship exists between temperature and dissolved oxygen (r2=-0.911). Also, Melanoides tuberculata and Lynmea natalensis have negative correlation with DO (r2=-0.836 and r2=-0.592 respectively) and Nitrate (r2=-0.896 and r2=-0.490 respectively). The presence and absence of some macro-benthic invertebrates in the study area is an indication of the impact of human activities on the reservoir; thereby requires a good management program in order to keep the relevance of the reservoir in its use for domestic purposes.