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

Abstract

Benthic macroinvertebrates 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 the diversity of some benthic macroinvertebrates in Ajiwa Reservoir. The study was conducted from September 2014 to August 2015. Benthic macroinvertebrate samples were collected using an Ekman grab at five different sampling locations once monthly. The samples were sieved using a set of Tyler sieves with mesh sizes of 2mm, 1mm, and 150μm, respectively, and transferred into labelled plastic storage bottles, preserved with 4% formalin prior to sorting and identification using keys. A total of 24 taxa from 1420 individual organisms were recorded, including 5 species each of Mollusca and Diptera, 1 species of Odonata, 4 species of Hemiptera, and 3 species each of Coleoptera, Oligochaeta, and Nematoda. The relative percentage composition of the major taxonomic groups in the overall macro-benthic population at the different stations revealed that the study area was inhabited by Oligochaeta (40.28%), Mollusca (24.08%), Diptera (19.29%), Odonata (5.78%), Coleoptera (3.94%), Nematoda (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 > station 3. Factors that influenced the abundance and distribution of invertebrates, including the nature of the water body, habitat richness and stability, substrate, trophic conditions, resource partitioning, and predation, as well as habitat differences observed in this study, acted singly or in combination to influence the variation in abundance of benthic macroinvertebrates in Ajiwa Reservoir.