Anyim River is an important tributary of Cross River that provides water for
various purposes to some rural communities in Ebonyi, Benue and Cross
River states of Nigeria. However, the river is polluted from anthropogenic
and naturogenic sources, which is worrisome. This study assesses the
responses of the phytoplankton community to changes in water quality as a
preliminary step toward mitigating pollution of the river. Water and
plankton samples were collected bimonthly from November, 2017 to
September, 2019 and then analysed in the laboratory following standard
procedures. The results showed that mean water temperature
(29.97±2.34oC), total dissolved solids (28.00±4.21mg/L), conductivity
(50.00±5.28µS/cm), carbon (iv) oxide (8.63±1.10mg/L) and transparency
(0.19±0.12m) were higher in the dry season. All the water quality
parameters varied significantly (p<0.05) between seasons except dissolved
oxygen, nitrate and transparency. Cyanophyta (487 cells/L) was the most
abundant phytoplankton during the dry season while Bacillariophyta had the
highest diversity (Hʹ=1.84) and species richness (d=2.53) in the wet season.
Principal Component Analysis (PCA) revealed that pH, transparency,
nitrate and phosphate favoured the abundance and diversity of
Bacillariophyta and Cyanophyta during dry season. The dominance of
Cyanophyta in dry season was an indication of poor water quality.