Comparative evaluation of bioaccumulation of heavy metals in plankton and water from Elechi Creek, Port Harcourt, Nigeria

Bioaccumulation of heavy metals (cadmium, Cd; chromium,Cr; lead, Pb; copper, Cu) in plankton and water from Elechi creek were studied for twelve months. Plankton and water samples collected using plankton net and bottles were analysed for heavy metals following standard method of APHA and the data obtained were subjected to statistical analysis. Results showed that plankton accumulated more heavy metals than water with the orders of magnitude, Cu> Cd > Cr >Pb and Cu > Cr> Pb> Cd for plankton and water respectively. The mean values of heavy metals in water were lower than the EPA, USEPA and WHO permissible limits for human consumption. Pb concentration in plankton differed significantly in station 4 while Cu differed seasonally with dry season values higher than wet season values unlike the heavy metal concentration in water. The higher bioconcentration factor (BCF) and the order, Cd>Pb>Cr> Cu observed showed that plankton has high potential to concentrate heavy metals. The dominance by Bacillariophyceae followed by Chlorophyceae and Cyanophyceae in species and abundance and the presence of indicator species, Cyclotella species , Melosira monoliformis and Navicula distans indicates pollution. This calls for awareness and constant assessment to avoid further contamination of the resources meant for human consumption. Keywords: Heavy metals, plankton, bioaccumulation, pollution, Elechi Creek