Influence of Limnological Factors on Macrophytic Diversity and Distribution in the Humic Freshwater Ecosystem of Eniong River, Itu, Nigeria

Aims: This research explores the relationships between key limnological variables and macrophyte structure, examining how changes in water quality parameters impact the composition and density of aquatic plant communities. Study Design: A stratified random sampling design was employed to ensure comprehensive coverage of the river ecosystem. Place and Duration of Study: The study was conducted on the Eniong River, a tributary of the Cross River, located in Itu Local Government Area of Akwa Ibom State, Nigeria. Sampling was conducted over a period of one year to capture seasonal variations. Methodology: A stratified random sampling design was employed to ensure comprehensive coverage of the river ecosystem. The river was divided into four zones based on geomorphological characteristics and land use patterns for collection of macrophyte and limnological data. Along each transect, five 1m2 quadrats were randomly placed for detailed macrophyte assessment. Limnological variables were conducted based on standard methods as described in APHA. Results: The pH values across the stations ranged from 6.15 to 6.71, indicating slightly acidic conditions in the humic waters of the eniong river. Nitrate levels ranged from 81.42 mg/L to 104.89 mg/L, significantly exceeding the WHO and NESREA limits of ≤10 mg/L whileShannon-Wiener values decrease from Station 1 (1.458) to Station 4 (0.5449), consistent with declining taxa richness and evenness.  Simpson’s diversity decreases from Station 1 (0.7463) to Station 4 (0.2567), reflecting reduced species diversity downstream. Dominance increased from Station 1 (0.2537) to Station 4 (0.7433), indicating a shift towards communities dominated by fewer, more competitive species downstream. The CCA analysis for surface water showed that DO, phosphate, TSS, BOD were negatively associated with Pontederia crassipes and Ipomea aquatica. Conclusion: The correlation between deteriorating water quality, particularly heavy metal contamination, and reduced macrophyte diversity underscores the need for better management strategies.