Osuebi, Emmanuel Chikezie2026-03-162026-03-162021-06Osuebi, E. C. (2021). Assessment of physicochemistry and plankton taxa of the Otamiri River System in Owerri, Imo State [Unpublished Master's Thesis]. Federal University of Technology, Owerri, Nigeriahttps://repository.futo.edu.ng/handle/20.500.14562/2372This thesis is for the award of Master of Science (MSc.) in Environmental ManagementPlankton could serve as bio-indicators of pollution in water bodies, and this makes them important in the assessment of water pollution.This study investigated the interactions of some physicochemical attributes and plankton abundance and diversity in the upper and middle reaches of the OtamiriRiver in Owerri, Imo State. Plankton samples were collected at four sampling locationsand identified through direct microscopy. Descriptive statistics, variation plots,ANOVA, Duncan Multiple Range test, and correlationwere used to analyze data at p<0.05 level. Mean levels of Dissolved Oxygen (DO), water temperature, electrical conductivity, and Total Dissolved Solids (TDS) (Sig. Fvalue=0.000 each), Biological Oxygen demand (BOD) (Sig. Fvalue=0.035), pH (Sig. Fvalue=0.025), Total Suspended solids (TSS) (Sig. Fvalue=0.004), turbidity (Sig. Fvalue=0.005), PO4 3- ions (Sig. Fvalue=0.029) and SO4 2- ions (Sig. Fvalue=0.003) all differed significantly across the sampling locations of the river at p<0.05. Phytoplankton abundance comprised of a total of 9 genera each of bacillariophyceae and cyanophyceae, 6 genera of chlorophyceae, 2 genera each of euglenophycea and xanthophycea, and 1 genus each of charophycea and pyrrophyceae.The most abundant diatom genus wasDiatomasp while that for cyanophyceae was Aphanizomenonflos-Aquae. Sampling location 3 (Ihiagwa/Umuchima) recorded the highest phytoplankton and zooplankton abundances(158 &7 cells/organisms/mL) while the pristine/control location 1 (Egbu) had the least abundance of 108 & 2 cells/organisms/mL respectively. Significant spatial inequality was observed in abundances of the cladoceran (Sig. Fvalue=0.030), xanthophycean and euglenophycean (Sig. Fvalue=0.011 each) taxa at p<0.05.Phytoplankton taxa were more diverse, with Margalef’s Index (I) range of 2.56-5.03, than zooplankton taxa with I values ranging from 0.51-1.44. DO correlated with euglenophyceae (r=-0.679), xanthophyceae (r=-0.673) (p<0.05), and chlorophyceae (r=-0.747) (p<0.01), and TSS correlated with bacillariophyceae (r=0.629) (p<0.05).Low abundance of plankton recorded in the studymost probably reflects a perturbed aquatic ecosystem lacking in vital nutrients and other factors necessary for a thriving bioticcommunity.enAttribution-NonCommercial-ShareAlike 4.0 InternationalPlanktonbiotic indexphysicochemical parametersOtamiri RivernutrientsDepartment of Environment ManagementMaster’s Thesis