Phytoplankton assemblage and environmental variables in Ogun State Coastal Estuary, Nigeria

Abstract

The distribution and composition of estuarine phytoplankton species provide prerequisite to the understanding of the dynamics of aquatic ecosystem and its diagnostic assessment. The present study was on the relationship between phytoplankton assemblage and environmental variables. It was carried out between February and July, 2014, in three distinct zones in Ogun State coastal estuary: brush park (Zone I), open water (Zone II) and wetland (Zone III). Data collected were subjected to community structure analysis using trophic state index, species richness and diversity indices. A total of 42 phytoplankton species belonging to six taxa, Bacillariophyceae, Chlorophyceae, Cyanophyceae, Pyrrhophyceae, Chrysophyceae and Euglenophyceae were identified with a clear dominance of Chlorophyceae 8064 no./ml, 9072 no./ml and 9324 no./ml were recorded in Zones I, II and III respectively. The mean values of water quality parameters were recorded: temperature (28.34±0.07 ºC); pH (6.59±0.12); electrical conductivity (503.44±33.99 μS/cm); dissolved oxygen (9.59±0.13 mg/L); salinity (0.45±0.04 ‰); phosphate (0.26±0.02 mg/L); nitrate (0.20±0.02 mg/L); transparency (31.47±0.17 cm) and chlorophyll a (0.033±0.01 mg/L). Analysis of variance (ANOVA) showed no significant difference (p>0.05) in the water physical and chemical parameters. Canonical correspondence analysis (CCA) showed that the environmental variables had varying impact on the distribution and abundance of phytoplankton species.

Keywords: Micro-algae, physico-chemical parameters, brackish environment, Ogun State