PHYSICOCHEMICAL CHARACTERISTICS AND PHYTOPLANKTON COMMUNITY STRUCTURE OF ADOFI RIVER, NIGERIA

Abstract

ABSTRACT

This study assessed the physicochemical characteristics and phytoplankton community structure of the Adofi River, Nigeria, across three sampling stations over a twelve-month period. Standard analytical procedures and microscopic examination were employed to determine water quality parameters and phytoplankton composition, abundance, and diversity, with spatial variations evaluated using one-way ANOVA. Most physicochemical parameters showed no significant spatial variation (one-way ANOVA, p > 0.05), except sulphate (p < 0.05), while temperature (26–30 °C), dissolved oxygen (5.47–6.50 mg/L), and moderate BOD₅ levels (2.28–2.95 mg/L) indicated low organic pollution and generally good water quality with limited eutrophication; additionally, 2,653 phytoplankton individuals comprising 117 species, 37 families, 9 classes, and 6 divisions were recorded, with Ochrophyta (46.63%) and Charophyta (38.94%) dominating, and Cyanobacteriophyta (7.95%) increasing downstream. Overall, the dominance of diatoms and charophytes reflects favorable ecological conditions, while the presence of pollution-tolerant taxa at low abundance suggests early but non-critical nutrient enrichment, indicating that the Adofi River remains in good ecological condition but requires continuous monitoring to prevent future degradation.