Biodiversity Assessment of Some Benthic Macro Invertebrates in Ajiwa Reservoir, Katsina State, Nigeria

Abstract

Benthic macro invertebrates represent a useful tool in the evaluation of environmental quality through studies of the structure of communities and their relationship to anthropic activities within a reservoir. The objective of this study was to assess diversity of some benthic macro invertebrates in Ajiwa reservoir. The study was carried out from September, 2014 to August, 2015. Benthic macro invertebrate samples were collected with the aid ofEkman grab at 5 different sampling locations once monthly. Samples collected were sieved with a set of Tyler sieves of 20cm diameter and mesh sizes of 2mm, 1mm, and 150μm respectively and transferred into labelled plastic storage bottle and preserved with 4% formalin prior to sorting and identification with the aid of some keys. Twenty four (24) taxa from a total of 1420 individual’s organisms were recorded. These include 5 species each of Mollusca and Diptera, 1 species of Odonata, 4 species of Hemiptera and 3 species each of Coleoptera, Oligochaete and Nematoda. The relative percentage composition of the major taxonomic groups to the overall macro benthic population at the different stations revealed that the study area was inhabited by Oligochaete (40.28%), Molluscs (24.08%), Diptera (19.29%), Odonata (5.78%), Coleoptera (3.94%), Nematodes (3.38%) and Hemiptera (3.24%).The indices of general diversity (H), evenness (E), dominance and relative abundance were in the following order of increasing magnitude: station 5 > station 1 > station 4 > station 2 and > station 3 respectively. Factors which influenced the abundance and distribution of invertebrates; including the nature of the water body, habitat richness and stability, immediate substrate, tropic condition, resource partitioning and predation coupled with habitat differences observed in this study, acted singly or in combination to influence the variation in abundance of benthic macro invertebrate of Ajiwa Reservoir.