Bacterial Indicators of Contamination in Highly Impacted Segment of Tropical Lagoon, Southwest Nigeria

Abstract

Increasing deterioration of coastal waters is a major public health concern in many regions of the developing world. This study investigates the impact of water quality on the proliferation of bacterial pathogens in surface water, sediment and tissues of fish, Sarotherodon melanotheron from the Makoko axis of Lagos Lagoon. Analysis of physicochemical characteristics and microbial quality of samples followed standard methods and procedures.  Measured water quality parameters (water temperature, turbidity, pH, salinity and dissolved oxygen) which showed no significant variation (p>0.05) across study stations were within the Nigerian Federal Environmental Protection Agency set limit The highest total bacterial count (TBC) (214.09±43.95 x 10⁵ CFU g^-1), total coliform counts (TCC) (91.15±15.05 ×10⁴ CFU g^-1) and total faecal coliform (TFC) (36.22±12.98×10³ CFU g^-1) were recorded in fish muscle tissue while the lowest TBC (52.39±39.72 x 10⁵ CFU ml^-1), TCC (33.45±33.94 ×10⁴ CFU ml^-1) and TFC (0.19±0.18×10³ CFU ml^-1) were recorded in water sample. The bacterial species with the highest percentages of occurrence in water, sediment, fish gill and fish muscle tissue were Klebsiella pneumoniae (22.11 %), Enterobacter aerogenes (32.37 %), Escherichia coli (32.97 %) and E. coli (29.00 %) respectively. A very strong positive correlation (r = 1.00) was obtained between TBC in water and salinity as well as with dissolved oxygen levels. Likewise, the TBCs in fish parts (muscle tissue and gill) were positively correlated with the water temperature and turbidity. On the other hand, a negative correlation was obtained between pH and TBC in fish muscle tissue (r = -0.81) as well as with fish gut (r = -0.77). The relatively high counts of pathogenic bacteria species recorded during the study have serious public health implications.