Interrelationships Among Phytoplankton Communities Structure in the Calabar River Ecosystem

Authors: *Ogidiaka-Obende, E., Kaine, E. A. And Ndinwa, G.C.C.

DOI Info: http://doi.org/10.5281/zenodo.18061710

ABSTRACT

Phytoplankton communities are essential bioindicators of aquatic ecosystem health due to their sensitivity to environmental variations. This study examined the interrelationships among phytoplankton community structures across spatial and seasonal gradients in the Calabar River ecosystem, Southern Nigeria. Surface water samples were collected from four stations during the wet and dry seasons in 2020. Standard methods were used for phytoplankton enumeration and identification whereas inter-species relationships were analyzed using Pearson’s correlation matrices and heatmap visualization in R and python environments. The results revealed marked seasonal and spatial differences in phytoplankton composition, with dominant taxa including Cyclotella comta, Skeletonema costatum, Bacillaria paradoxa, Penium sp., Eudorani elegans and Oscillatoria sp. During the wet season, strong positive correlations (r = 0.74-0.99) were recorded among most species, suggesting co-occurrence and mutual ecological tolerance among species sharing similar environmental preferences. In contrast, the negative correlation (r = -0.83 to -0.29) between Staurastrum rotula and Cyclotella comta suggested competition for resources under fluctuating hydrological conditions. The dry season analysis revealed a shift in dominance, with centric diatoms and desmids co-dominating and cyanobacteria showing reduced association strength. Spatially pronounced heterogeneity was observed among the stations, with Eudorina elegans and Oscillatoria sp. dominating the upstream zone, whereas Skeletonema costatum and Cyclotella comta thrived at the mid-stream and downstream zones. The study established that phytoplankton interrelationships are important ecological indicators for water quality assessment.

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