Response of phytoplankton to seasonal changes in some water quality parameters in Anyim River, Ebonyi State, Southeast, Nigeria

Abstract

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±2.34^oC), 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.