Effect of industrial effluent on physico-chemical parameters and macro-invertebrate community in Napoleon gulf, Lake Victoria.

Abstract

The study assessed the effect of industrial effluent on the physicochemical water parameters, macro-invertebrate abundance, composition and diversity in Napoleon Gulf Lake Victoria Selected physico-chemical water characteristics at selected sampling points were determined in-situ while as nutrients (TN & TP) and Biological Oxygen Demand were determined in the laboratory using standard methods (Wetzel. et al, 2000). Triplicate macro invertebrate sample at each sampling point were collected using a ponar grab identified based on morphological appearance using identification keys. Physico-chemical results revealed that Dissolved oxygen was high at offshore transect with a mean value of 7.09 ± O. 17mgL in March low at inshore in February with a mean value of 3.63 ± 0.92mgL, pH was generally alkaline at all transects with mean values ranging from 7.06 ± 0.02 to 9.12 ± 0.05. BOD5 was high at inshore in April with a mean: value of 13.73 ± 1.80mgVl and low at offshore in March with 6.35 ± 1.01mgL. TN and TP was: high at mid-shore with mean values of 2905.08 ± 2156.3 µgLl (April) and 194.89 26.38: µgL-1 (Feb) respectively. A total of five (5) taxa of benthic macro invertebrates identified to family level were recorded. Of which Annelida recorded 766% with Hirudnea spp (1 008 ± 558m-2) and Oligochaete spp ('.154 ± 6.1m-2) were numerically dominant and abundant, no Dipteran was recorded at inshore. Bivalvia taxa dominated mid-shore transect with 39.2% i.e. Byssanodonta spp (976 ± 149m -2) and Sphaerium spp (938 ± 209m -2) while Ephemeroptera (Povilla adusta spp, 154 ± 85m-2) was the least with only 3.2%. At offshore, Ephemetopterans were not recorded while Annelids (78.3%) were the most dominant with Hirudinea spp (2451 ± 641 ma) and Oligochaete spp (2190 ± 1106m-2). Hence, low abundances at inshore indicated that its less polluted compared to offshore and mid-shore transects. Conclusively, most of the macro-invertebrates recorded during the study were those tolerant to pollution. Therefore, the management authorities should put up abatement policies and standards to protect aquatic ecosystems from pollution by humans.