Evaluation of Heavy Metal Bioaccumulation by Phytoplankton and Water, Sombriero River, Port Harcourt

Abstract

The heavy metal bioaccumulation by phytoplankton and water in Sombriero River, Port Harcourt was determined. Heavy metals and phytoplankton samples were collected from four different locations using plastic bottles and plankton net of 55um mesh size between February and April,2020. Plankton and water samples collected from the locations were analyzed for phytoplankton and concentration of the five heavy metals, iron (Fe), copper (Cu), cadmium (Cd), lead (Pb) and chromium (Cr) in water and plankton following the standard method. A total of 38 species with 2,888 individuals’ phytoplankton from the families, Bacillariophyceae, Chlorophyceae, Cyanophyceae, Chrysophyceae and Euglenophyceae were recorded during the study period. The mean concentrations of the heavy metals (mg/l), Fe, Cu, Cd, Pb and Cr in water and plankton are 0.51±0.09, 0.29±0.03, 0.01±0.00, 0.05±0.03 and 0.39±0.11 while that of plankton (mg/g) were 1.90±0.23, 0.92±0.11, 0.69±0.20, 0.35±0.13 and 0.83±0.14 respectively with the order of concentration Fe>Cr>Cu>Pb>Cd and Fe>Cu>Cr>Cd>Pb for water and plankton respectively. The heavy metal concentration in the plankton was observed to be higher than that of the water. All the metals studied (Fe, Cu, Cd, Pb and Cr) exceeded the permissible limit of environmental protection agency (EPA) and maximum permissible limit (MPL) for water but below the permissible limits for plankton except Cd. It is evident that Sombriero River is under stress considering the heavy metal concentration in the water which exceeded the recommended permissible limits of EPA, WHO and the presence of the pollution indicator species, Cyclotella species, Melosira monoliformis and Navicula distans and the families Bacillariophyceae, Cyanophyceae and among others. It is therefore recommended that adequate measures should be taken to regulate the level of anthropogenic activities especially the illegal ones such as bunkering, use of pesticides, herbicides and other obnoxious chemicals especially in agricultural operations.