Isolation and enumeration of bacteria present in Lagos Lagoon, Nigeria

Abstract

The study was conducted to isolate and enumerate microorganisms present in Lagos Lagoon, Nigeria. Samples of water and sediment were collected during the wet and dry months from twelve selected stations (NIOMR Jetty, Atlas Copco, Sagbon Kwoji, Folawiyo Apapa, Liverpool, Ijora, Ebute Ero, Okobaba, Unilag front, American Embassy, Lekki Shoprite, and Lekki Parkview) along the Lagoon using standard procedures. Determination of bacterial loads and composition in both water and sediment samples were done using standard microbiological procedures. Results revealed the presence of heterotrophic bacteria (THB) in all sampling stations across both seasons, with the highest occurrence (1.74 x 10⁶ cfu/g) recorded in sediment sample from Ijora Station. Unilag font had the lowest microbial count of 1.32 x 10¹ cfu/g during the wet season while Liverpool recorded the highest count (3.9 x 10⁵ cfu/g) in the same season. Other seasonal results revealed mean total coliform count of 4.3 x 10¹ cfu/g, faecal coliform count of 9.04 x 10² cfu/g, Salmonella shigella count of 3.7 x 10² cfu/g and Vibro count of 6.55 x 10² cfu/g in the wet months. Results for the dry season months were 4.31 x 10² cfu/g, 6.76 x 10² cfu/g, 5.66 x 10² cfu/g and 5.41 x 10² cfu/g for total coliform, faecal coliform, Salmonella shigella and Vibro counts respectively. Generally, growth on selective media showed THB count in water to be 2.0 x 10⁵ cfu/g while that in sediment was 3.9 x 10⁵ cfu/g which were observed to increase significantly during the wet season. This increase in THB values may likely be due to changes in hydrographic parameters, flooding, and human activities like sewage dumping. The Liverpool Station consistently showed high microbial counts from the beginning to the end of the study in both water and sediment samples. Periodic environmental assessments are recommended to monitor pollution levels and conduct impact assessments.