ABSTRACT
Wetlands are one of the most productive ecosystems in the world as they are important economically in fishing, agriculture, husbandry, reed production, ecological tourism and educational and scientific research. Heavy metal pollution has resulted in unprecedented degradation of these productive ecosystems thereby limiting their functionality and productivity. The aim of the study is to evaluate the heavy metals and benthic invertebrate community of wetlands in Warri, Delta State, Nigeria. This study was carried out in four selected Wetlands from three Communities in Warri South Local Government Area, Warri, Delta State. Heavy metals of the water and sediment were analyzed following standard methods while pollution indices were computed using Pollution load index (PLI), Index of geoaccumulation (Igeo) and contamination factor (CF). Sediments and macrobenthic invertebrates’ samples were collected monthly between 09:00 am to 15:00 pm at four stations using standard methods and procedures, macrobenthic invertebrates were identified using appropriate keys. Results from the study indicated significant (p < 0.05) spatial and temporal variations in the concentration of heavy metals in water and sediment, with Iron, Lead and Cadmium exceeding World Health Organization permissible limits for drinking water. Heavy metals in water followed the order Fe > Zn > Cu > Cr > Pb > Cd and that of sediment followed Fe > Zn > Cu > Pb > Cr > Cd,’’ with higher concentrations of heavy metals obtained in sediment than in water. Pollution Load index (PLI) revealed PLI values of 0.7723, 0.7672, 0.7726 and 0.7768 in stations 1, 2, 3 and 4 respectively. A total of ten (10) benthic invertebrate groups comprising 62 taxa and 394 individuals were collected during the study period. This comprised of 175 individuals of gastropoda (44.4%), 117 individuals of oligochaeta (29.7%), 53 individuals of decapoda (13.5), 16 individuals of diptera (4.1%) and 15 individuals of crustacea (3.8%). Continuous assessment of heavy metal pollution in water and sediment of Warri wetlands, including the macrobenthic fauna distribution is recommended to provide information on the pollution status of the wetlands.
