A Comparative Study of the Periphyton on Eichhornia crassipes and Phytoplankton Communities: An Overview of Environmental Conditions at Ejirin Part of Epe Lagoon, South Western Nigeria

Abstract

Periphyton and phytoplankton communities were compared and investigated in view of the environmental conditions at Ejirin part of Epe lagoon, from Dec. 2012 – May, 2013. This was to evaluate the effect of the environmental characteristics on the biotic communities. Surface water temperature correlated significantly with rainfall (r 0.855*; P < 0.05), surface water Chl. a (r = 0.817*; P < 0.05) and with periphyton individual (r = 0.745). The water pH remained acidic throughout the study period (pH < 6.6) with a mean value of 6.39. Transparency values were high in the dry months and low in the wet months, with the strong significant correlation with the periphyton and phytoplankton individual (r =0.844*; P < 0.05) and (r = -0.887*; P < 0.05) respectively. Total suspended solids has a mean value of 61.02mg/L, and correlated significantly with periphyton individual (r=0.836*; P < 0.05), and strongly correlated with phytoplankton individual and rainfall (r =0.791 and 0.678) respectively. The micronutrients varied throughout the study periods with reactive nitrate (NO3-N ≤ 0.32mg/L), reactive phosphate (PO4-P ≤ 0.78mg/L), silicate (SiO3 ≤ 0.80mg/L), and sulphate (≤1.30mg/L). Sulphate correlated strongly with phytoplankton and periphyton individual (r=0.616 and 0.707) respectively. Five divisions were recorded in phytoplankton community with their percentage of occurrence: Bacillariophyta (82.45%), Cyanobacteria (9.99%), Chlorophyta (6.08%), Euglenophyta (1.32%), and Chrysophyta (0.12%), whereas four divisions were recorded in periphyton community with their percentage occurrence: Bacillariophyta (82.67%), Cyanobacteria (10.54%), Chlorophyta (5.64%), and Euglenophyta (1.15%). The PCA factor analysis revealed the importance of the followings: water temperature, pH, TDS, rainfall, sulphate, COD, BOD, nitrate, phosphate, salinity and, phytoplankton and periphyton individual to the future environmental analysis. Therefore, the periphyton community has shown a more promising tool in the event of environmental studies by responding significantly to most of the environmental parameters studied.