ASSESSMENT OF WATER QUALITY AND MACROBENTHIC FAUNA OF LAGOS LAGOON, LAGOS, NIGERIA

Abstract

The decomposition of biodegradable wastes in aquatic ecosystem is the main cause of organic pollution with its
consequent hazardous effects on the environment. Six stations in the Lagos lagoon were studied between July and
December, 2023. The aim was to evaluate the impact of biodegradable wastes on the water and benthic fauna of the
lagoon. Water and benthic samples were collected monthly at each study station using the Hydrobios water
sampler and the Van-veen grab respectively, and analyzed in the laboratory following standard procedures. The
analysis of variance (ANOVA) showed that there was no significant difference (P> 0.05) in values of the pH,
salinity, conductivity, turbidity and biochemical oxygen demand measured among the study stations, while
dissolved oxygen, total dissolved solids and total suspended solids showed significant differences (P< 0.05). A
total of 597 benthic macrofauna individuals comprising three phyla, four classes, four orders, eight families, eight
genera and eight species were sampled. The gastropods, Tympanotonus fuscatus dominated the benthic
macrofauna assemblage of the study area accounting for 56.0%. The phylum Arthropoda was represented by one
species Clibanarius africanus, recorded the least number of individuals, which contributed 0.05% of the total
number of individuals collected during the sampling period. The low abundance of the filter-feeding bivalves, the
highly sensitive arthropod species as well as Pachymelania aurita in the study area may be indicative of poor
water quality due to organic pollution.