Potential menace posed by invasive grass and water quality deterioration on macroinvertebrates structural distribution in a dam in North-Western Nigeria

Abstract

ABSTRACT Water bodies in the world have been studied for varied reasons based on their biota composition, diversity, and influence of environmental variables. A study was carried out to ascertain the probable menace posed by Typha grass and some selected environmental variables on the composition and diversity of benthic macroinvertebrates of Kalgwai Dam, Jigawa State, Nigeria. Three (3) distinct sites were selected for the study. Water and macroinvertebrates samples were collected once in a month on each sampling expedition for a period of four (4) months between January and April, 2018, using standard techniques. Among the sampled months, physico-chemical variables were significantly different (p < .05), while no significant difference existed for all the physico-chemical variables (p > .05) except for electrical conductivity, salinity, total dissolved solids, and BOD5. A total of 260 benthic macroinvertebrate specimens comprising of 20 taxa belonging to 9 orders and 20 families were recorded during the study period. Site 2 harbors more macroinvertebrates than other sites and Gastropoda was the most occurring taxa in the study area with Site 2 having the highest abundance among the taxa sampled during the study period. Significant difference (p < .05) was noticed in abundance (number of individuals) among the sites. Species number (taxa) and abundance (number of individuals) were significantly highest in Site 2. Shannon diversity of macroinvertebrates taxa was lowest in Site 1 (0.98 ± 0.28). Analysis of variance (ANOVA) performed showed no significant differences in the indices calculated (p > .05) except for Evenness. Canonical correspondence analysis (CCA) showed a weak relationship between macroinvertebrates composition/abundance and the selected physico-chemical variables. Species such as Corbucilidae, Chironomus sp., Potadoma sp., Unio sp. portray the characteristics of potential bioindicators due to their association to prevailing environmental condition of the sampled sites. Cluster analysis (Bray-Curtis) similarity showed no marked pattern of clustering in the dam. The study revealed that incessant anthropogenic activities and high density of Typha grass in Kalgwai Dam have a deteriorating effect on the structural composition, abundance and diversity of macroinvertebrates in the dam.