Response of Macrobenthic Invertebrate to Organic Carbon and Particle Size in Lagos Lagoon, Nigeria

Macrobenthic fauna communities are important constituents of soft bottom marine ecosystems which inhabit the bottom environments playing a key factor in controlling structure and functioning of the aquatic environment. Lagos lagoon is the most exposed lagoon to anthropogenic influence in Nigeria coastal lagoon system. Bimonthly sampling was carried out in the Lagos lagoon from September 2014 - July 2016 for water and sediment in twenty – four stations to examine response condition of benthic communities to measures of water quality and sediment quality in Lagos lagoon in order to understand the benthic condition of the aquatic environment. A range of 9 – 91% for sand, 7 – 25% for silt, 0 – 73% for clay while a range of 0 – 4.77 was observed for TOC. The Diversity (H,) richness (d) and evenness (j) were positively correlated with the silt sediment particle size and. Kruskal-Wallis test showed that there was significant difference (p<0.05) between species richness and diversity at all sampling stations. Analysis of variance (ANOVA) showed no significant difference (p>0.05) in mean percentage particle sizes and TOC recorded at the stations but was significant (p<0.05) between TOC and macrobenthic invertebrates. The overall low diversity of macrobenthic fauna observed was attributed to anthropogenic activities majorly industrial dredging and local sand mining which altered the sediment characteristics of the aquatic ecosystem. Assessments of human induced stressors in the lagoon provided information useful for strict regulations and environmental policies to help prevent the aquatic environment from continuous deterioration hence, causing more loss of biodiversity. Responses of macrobenthic invertebrates to measured variables showed that there are high abundance and diversity of ecological groups of sensitive species majorly distributed around the slightly disturbed zones of the study area. In summary, variables examined in this study showed that the total organic content does not have a depleting effect on the abundance of macrobenthic invertebrates because the values are within permissible limits but the particle size characteristics present in this study showed good environmental indicator for evaluating macrobenthic invertebrate responses to stress pattern in water bodies along the coastal areas surrounded by various human activities.