The pollution status and effects of seasonal changes in rivers within Imo River Basin, Southeastern Nigeria

Abstract

The pollution status and effects of seasonal changes in rivers within Imo River basin were studied between October 2015 and September 2016. Water samples and 4 species of fish samples were collected from seven rivers: Otanmiri, Nwaorie, Njaba, Blue Lake Oguta, OrashiOpuomo and AbubaUnuchi, using suitable sterile containers. The water and fish samples were analysed bacteriologically using culture technique and the method of (1) for physico-chemical parameters. The findings revealed that 11 genera of bacteria Staphylococcus species, Streptococcus faecalis, Micrococcus species, Aeromonas species, Vibrio species, Salmonella species, Proteus mirabilis, Escherichia coli, Flavobacterium species and Klebsiella species were present in the water and fish samples examined. The total heterotrophic bacteria count (THBC) of the rivers during the raining season ranged from 2.3 x 106 to 2.9 x 106cfu/ml and 2.02 x 105 to 2.6 x 105cfu/ml in the dry season. For the fish samples, the THBC ranged from 1.86 x 105 to 2.4 x 105cfu/ml in the raining season and increased to 2.3 x 105 to 2.8 x 105cfu/ml in the dry season. The physico-chemical parameters of the watersamples: cadmium, lead, mercury, nitrate, sulphate, phosphate and copper were found to be higher than WHO standard for drinking water, especially during the dry season. The prevalence of physically observed fish diseases generally increased from 35.6% percent in the raining season to 74.4% in the dry season. The study has established high pollution of rivers within Imo river basin and adverse effects of seasonal changes on aquatic organisms in the rivers due to pollution.