Seasonal changes in the abundance of benthic macroinvertebrates & physico-chemical condition of Moussa Stream Bida, Nigeria

Abstract

Seasonal changes in the abundance of benthic macroinvertebrates and physico-chemical condition of Moussa Stream, Bida Nigeria, were studied monthly from January to August 2017. Macroinvertebrates were sampled using modified kick sampling techniques. Three different sampling stations were selected along the course of the Stream. The results from the stream showed that water temperature (24.9-27.5⁰C), Depth  (14.7-45.8cm), Flow velocity (0.14-0.23m/s), Biochemical oxygen demand (2.0-7.0mg/L), pH (6.33-8.6), Conductivity (20-63μ/cm), Alkalinity  (8-30mg/L), Turbidity (61-285NTU), Nitrate (0.87-3.85mg/L) and Phosphate (0.31-1.01mg/L) were within the maximum permissible limit (WHO, SON) except Dissolved oxygen (3.1-10mg/L). Most of the parameters investigated with the exception of depth and flow velocity showed no significant difference (p>0.05) among all the sampling stations. Temperature, depth and flow velocity showed no significant differences with season. pH, DO, BOD5, Turbidity, Conductivity, Alkalinity, Nitrate, and Phosphate were significantly higher during wet season. A total of 471 individuals from 30 species and 20 families of invertebrates were recorded. The overall macroinvertebrates recorded from station 1, 2 and 3 were 166(35.24%), 149(31.63%) and 156(33.12%). Overall, there was significant difference (P<0.05) in number of individuals among the sampling stations. The abundance according to the Orders revealed that Coleopterans, Odonata and Hemipterans were the most common groups encountered. Ephemeroptera Diptera, Mollusca and Oligochaeta were sparingly found in all stations. The percentage and total number of individuals of macroinvertebrates recorded during the study period shows 67.09% (316 individuals) in dry season and the remaining 32.90% (155 individuals) were recorded in rainy season. CCA result correlated positively between species abundances and measured environmental variables. Low density of pollution sensitive macro invertebrates groups and the deteriorating water quality were implications of pollution stress caused by anthropogenic activities.

Key words: seasonal changes, macroinvertebrates, stream, Bida.