Exploring the spatiotemporal variation of environmental variables and phytoplankton community of Qua Iboe River, Akwa Ibom State, Nigeria

This study was conducted to determine the spatiotemporal variation of phytoplankton based on environmental variables of Qua Iboe River, Akwa Ibom State, Nigeria. Samples were collected monthly, from January 2020 to June 2021 in five locations. The water samples were evaluated for water temperature (WT), pH, dissolved oxygen (DO), biochemical oxygen demand (DOD5), nitrate (NO3), phosphate (PO-4 ), and ammonia (NH3) concentrations, using standard methodologies. The findings showed that the mean value of pH (locations 4 and 5), DO (all locations), PO-4 (locations 2 - 5) and BOD5 (locations 3 and 4) did not conform to environmental standards. Temporal mean values were ranged as WT 22.2 (July 2020) - 30.3oC (December 2020), pH 6.24 (September 2020) - 7.81(August 2020), DO 1.51 (April 2021) - 5.38mg/L (February 2021), Turbidity 5.31 (October 2020) - 23.2NTU (April 2020), NO3 2.02 (March 2020) - 10.5mg/L (June 2021), NH3 0.26 (February and March 2020) - 0.67mg/L (April and June 2021), BOD5 2.23 (February 2021) - 5.75mg/L (May 2021) and PO-4 2.27 (January 2021) - 8.32mg/L (April 2021). There were significant differences between the spatial and 4 temporal mean values (p< 0.05). A total of 44 phytoplankton species from five taxonomic groups were recorded. Bacillariophyceae was the most abundant (48.3 %), while Euglenophyceae was the least (3.2 %). Higher densities were recorded in location 1 (1584 cells/L) and October 2020 (657 cells/L), while the lowest were in location 3(1124 cells/L) and June (195 cells/L). The Shannon-Weiner index were moderate in location 3 (2.845) and higher in January 2020 (3.537); Margalef index were high in location 3 (2.420) and June 2020 (6.651), while Pielou's index were high in location 4 (0.973) and January 2020 (0.9656). It concluded that the human activities and season influence the water quality which in turn influences the phytoplankton community structure.