Ecological Status of Owan River, Southern Nigeria using Aquatic Insects as Bioindicators

Abstract

Aquatic insects are among the most directly affected and vulnerable organisms with respect to surface water pollution and used as bioindicators of water quality. The composition, distribution and diversity of aquatic insects in Owan River, southern Nigeria were assessed and influence of different physico-chemical factors were explored at four designated stations. Dissolved Oxygen (DO) (5.2 -7.8mgl-1) and biochemical oxygen demand (BOD) (1.64–2.60 gl-1) showed that the river was slightly aerated. A total of 38 taxa comprising of 1896 individuals were recorded during the study. Station 3 accounted for the highest number of individuals (530) while Station 1 had the lowest number of individuals (410). Order Diptera was the most ubiquitous insect taxa in the study with nine (9) species while order Plecoptera was sparingly represented by one (1) species Neoperla sp. Diversity index revealed that taxa richness (d) and diversity (H) were highest in Station 1 while Station 3 accounted for the lowest taxa richness and diversity. Ephemeroptera Plecoptera and Trichoptera (EPT) were highest in Station 3 and Station 1 had the least EPT value. Station 3 showed the lowest chironomid richness while Station 4 had the highest. The composition, distribution and diversity of aquatic insects in Owan River were affected by the nature of the streambed and physicochemical variables examined. Owan River can be said to be slightly clean water body rich in EPT organisms.

Key Words: EPT organisms, bioindicator, physico-chemical parameters, Owan River, Southern Nigeria.