Diversity of microalgal species and heavy metals concentration of selected earthen ponds water obtained from Eriwe Village Ogun-State, Nigeria

Abstract

Microalgae are morphologically diverse microscopic photosynthetic organisms whose isolation and identification present considerable taxonomic challenges. This study investigated microalgal diversity, physicochemical properties, and heavy metal concentrations in the water of an earthen pond in Eriwe Fish Village, Ijebu-Ode, Ogun State, Nigeria. Microalgal isolates were characterised by colonial morphology and microscopic cellular features. Physicochemical parameters were assessed using standard analytical methods, and heavy metal concentrations were quantified via Atomic Absorption Spectrophotometry (AAS). Data were expressed as mean ± SD; one-way ANOVA (p < 0.05) was used for statistical comparisons, and heatmap visualisation was generated using Python. Microalgal growth increased from 3.50×10³ (Day 4) to 21.25×10³ CFU/mL (Day 14), leading to an increase in F-values from 12.87 to 32.18. Lead (Pb) was the most critical contaminant, averaging 59.83 ± 2.56 ppm, approximately 5,983× the WHO permissible limit (0.01 ppm), peaking in Pond 2 (64.56 ppm). Eight microalgal species identified as Chlorella, Oscillatoria, Scenedesmus, Cladophora, Anabaena, Phormidium, Microcystis, and Navicula, spanning classes Chlorophyceae, Bacillariophyceae, and Cyanophyceae, were identified. The pond water sustains a taxonomically diverse microalgal community; however, alarmingly elevated lead concentrations represent a significant public health and ecological risk requiring urgent remediation.