ABSTRACT
This study which is to determine the physico-chemical characteristics of water, sediment and invertebrate fauna of Benin River at Koko, Delta State of Nigeria was carried out monthly between May 2015 and April 2017. Water samples for physico-chemical analysis were collected in clean sterilized plastic bottles with lid sediment samples were collected using Eckman grab. Benthos samples were collected from sediment using Eckman grab and by uprooting and dusting the roots of bankroot biotopes and the roots of floating Eichhormniacrassipes in a bucket of water. Sesarma crassipes samples were collected mainly by uprooting and dusting the roots of Eichhornia crassipes in a buckect of water devoid of formaldehyde. The Sesarmacrassipes samples were kept fresh without the addition of any preservative and were analysed in the same day of collection for heavy metals determination while the benthos samples were preserved in a plastic sample bottle with 10% buffered formaldehyde. The zooplankton were collected using a 55µm mesh size hydro-bios plankton net and fixed with 4% buffered formaldehyde. All parameters determined in water, sediment and Sesarmacrassipeswere analysed following standard methods (APHA 1998). The environmental variables measured in water samples were air temperature (27-30oC) water temperature (25-29oC), transparency (134cm-175cm), turbidity (0.0-39.0 NTU), conductivity (10.0-1180µS/cm), Total Dissolved Solids (15.9-637.2mg/l), Suspended Solids (2-43mg/l), Total Solids (21.6-644.2mg/l), pH (5.3-8), Alkalinity (6-20mg/l), Dissolved Oxygen (1-11.8mg/l), Biological Oxygen Demand (0.2-13mg/l), chloride (5-536.5mg/l), nitrate (0.98-6.96mg/l), sulphate (3-45mg/l), phosphate (0.06-0.48mg/l), zinc (0-0.77mg/l), Lead (0-0.05mg/l), Iron (0.18-3.22mg/l), manganese (0.02-0.63mg/l), copper (0.05-0.27mg/l), nickel (0.01-0.5mg/l), vanadium (0-0.062mg/l) and Oil & Grease (0.62-3.11mg/l). some of the parameters measured in sediment were pH (3.3-7.2), conductivity (150-710), nitrate (3.55-26.85mg/kg), zinc (4.12-7.12mg/kg), cadmium (0-0.08mg/kg), manganese (0.74-3.34mg/kg), lead (0.14-0.75mg/kg), iron (13.13-29.21mg/kg), chromium (0.12-1.13mg/kg), nickel (0-2.17mg/kg), vanadium (0-0.92mg/kg) and Oil & Grease (4.6-14.5mg/kg). The heavy metals determined in Sesarma crassipes were Zinc (0.02 - 5.13mg/kg), lead (0.04 - 1.44mg/kg), iron (10.43 - 39.54mg/kg), manganese (0.27 - 1.33mg/kg), copper (0.95 - 2.45mg/kg), nickel (0.03 - 3.62mg/kg), vanadium (0 – 0.12mg/kg), cadmium (0 - 0.017mg/kg) and chromium (0.002 - 0.26mg/kg). The invertebrate fauna was composed of 30 species with 5319 individuals. This was comprised of 16 species with 2093 individuals of zooplankton and 14 species with 3226 individuals of benthos.
