Abstract

Lagos lagoon is the largest of the eight lagoons that make up the lagoon systems of Nigeria and probably the most exposed to anthropogenic influence. The pollution status of the Lagos lagoon is generally attributed to the direct discharge of waste (domestic and industrial) and the contribution from rivers, creeks and drainage canals that empty into the Lagoon at different points. The paucity of information on the pollution status of water bodies that feeds the Lagos lagoon informed this present study. Investigation into the hydrochemistry and benthic macrofauna of Ogbe creek that drains through the main land of Lagos and empty into the Lagos lagoon was carried out. Fortnightly, sample collections between March and August 2002 at three stations along a 2 km stretch of the creek within the University of Lagos were used for the study. The hydrogen ion concentration ranged from 5.4 to 9.4. The electrical conductivity, salinity, alkalinity, nitrate, phosphate, dissolved oxygen and biochemical oxygen demand ranged between 3.65 ± 3.07 to 3.96 ± 3,22 Sµcm^-1; 0.51 ± 0.64 and 1.01 ± 0.96 ‰; 33.3 ± 23.2  and 60 ± 32.79 mgl^-1; 4.12 ± 0.17 and 7.46 ± 1.02 mgl^-1; 1.93 ± 0.53 and 3.65 ± 1.02 mgl^-1; 2.83 ± 1.42 and 4.65 ± 0.59 mgl^-1 and 7.96 ± 1.99 and 8.13 ± 1.61 mgl^-1, respectively. The high BOD₅, nitrates and phosphates values are indicative of a perturbed environment. A total of 246 organisms belonging to 16 benthic taxa, 13 genera, 12 families, 8 orders and 4 phyla were collected during the study period. Chironomid larvae and the Naidid worms were the most abundant groups. They accounted for 25.61 and 22.76%, respectively, of the total macrobenthic count. The low number of taxa and numerical abundance of pollution indicator macrobenthos in the study area reflected a perturbed creek.

Key words: Hydrochemistry, benthos, university of Lagos, Ogbe creek, Nigeria.