| dc.description.abstract | Physico-chemical and sediments are critical aquatic habitat resources for macroinvertebrates. Macro-habitats are altered through oxygen and food availability alteration. Distribution of macroinvertebrates in responses to physico-chemical characteristics and sediments are less understood in rivers. However, influence the abundance and distribution of macroinvertebrates. Physico-chemical and sediments data; and how this influence macroinvertebrate is key to understanding their dynamics in Isiukhu River. This study evaluated the physico-chemical parameters and substrate characteristics on the abundance, diversity and spatial distribution of macroinvertebrates in Isiukhu River. Specifically, the study (i) determined physico-chemical parameters along the river (ii) quantified the sediment grain size along river (iii) analysed abundance and spatial distribution of macroinvertebrates, and (iv) evaluated the relationship between physico-chemical parameters, substrate characteristics and macroinvertebrate distribution and composition along river. The study was conducted between March 2018 and March 2019. Samples were taken from three zones that were divided into 10 sampling sites; Upstream (Ichina 1, Ivakale 2, Kimangeti 3 and Senyende 4); midstream (Shirere 5, Rosterman 6 and Mwibatsilo 7); downstream (Shibeye 8, Mutono 9 and Ekero 10). Temperature, dissolved oxygen, pH, salinity, percentage saturation oxygen, conductivity and turbidity were measured on site using Hydro Lab. H2O sample were taken for Total Suspended solids, Nitrates and phosphates determination in the laboratory. Sediments were collected using shovel and Ekman Dredge sampler while benthic macroinvertebrates were collect using a Kick-Net. Macroinvertebrates were preserved in 70% alcohol and transported to the lab for identification. Dried sediment samples were separated using a Retsch Sieve Shaker with from 0.063 to 15mm mesh sizes, weight of each fraction was measured and recorded. SPSS version 23 was used to calculate the mean values of physico-chemicals and GRADISTAT 9.1 to sediment grain sizes. Diversity and eveness were calculated using Shannon diversity index. Temperature, conductivity, turbidity, salinity, pH and Oxidation Reduction Potential from the upstream to downstream. The upstream sediments were very coarse gravelly; the downstream sediments are very fine sand indicating that the sediments get finer downstream of Isiukhu River. Rosterman had the highest mean sediment grain size (9.97 mm), and Senyende (0.56 mm) had the least. Upstream sampling sites were dominated by Vellidae, Gyrinidae, Gerridae and Notonectidae, midstream sites were dominated by Vellidae, Gerridae, Notonectidae, Cybaeidae, Heptagenidae and Belostomatidae and the downstream by Vellidae, Gerridae, Notonectidae, Cybaeidae, Heptagenidae and Dictynidae. A total of 637 individual of macroinvertebrates were collected from upstream sites, midstream had 248 individuals while the downstream had 108 individuals. Highest mean abundance (100±9.2) was recorded at Kimangeti (upstream) while the least at Mutono (11±0.7) downstream. H= 2.2177 was greater at Kimangeti (upstream) while lowest at Ekero (1.2012) downstream. Physico-chemical and sediment accounted for 54.8% and 28.7% respectively of variability of macroinvertebrates. Study shows that physico-chemical and sediments influences macroinvertebrates abundance and diversity in Isiukhu River. | en_US |
