The aim of the paper is to identify macroinvertebrates distribution in response to induced stressors and physico-chemical parameters of water and sediment. The species composition of macrobenthic invertebrates as well as the physico-chemical characteristics of Badagry creek was investigated monthly. Six sampling stations selected based on different levels of human activities along the creeks stretch and samples were collected monthly from September 2006 to February 2007. The fluctuations of some of the physical and chemical parameters such as pH, dissolved oxygen, BOD and total organic carbon appeared to have been influenced by activities along the study stretch. Analysis of variance (ANOVA)  for all parameters showed no significant differences (P > 0.05) in the parameters but  Post hoc tests analysis using Duncan showed that there was a significant difference (P = 0.05) in the mean total of some of the parameters. pH, clay, sand and gravel were significantly correlated with other parameters while canonical correspondence analysis (CCA) model showed that the environmental variables correlated with significant part of the variations in the individual species abundance and it revealed that dominant species were found to be significantly correlated with dissolved oxygen, total dissolved solids, sand and pH.

A six months investigation on the environmental impact of fish cage culture on surface water and sediment of the Lagos lagoon were studied monthly from February 2011 to July 2011. Samples were collected from three stations, 1 (upstream of cage culture site), 2 (cage culture site) and 3 (downstream of cage culture site) between 07:00 and 11:00 h. During this period, the surface water ranged between 23.34 ± 3.39-23.79 ± 1.52°C, depth ranged between 0.91-0.99 m. The lowest DO value and highest biological oxygen demand (BOD) (mean = 4.43 and 6.00 mg/L) was recorded at station 2, respectively. These values may be due to the required oxygen used to break down fish wastes and excess feed pellets from the fish cage at this station. The analysis of variance test on parameters of water samples collected showed no significant difference (p>0.05) among the three study stations while the analysis of variance test on the sediment samples collected showed significance difference (p<0.05) in ammonium and total organic carbon among the study stations. There is a need for future development initiatives to focus on best management practices (BMPs) for low impact, ecologically sound and sustainable aquaculture.

This study was focused to assess contamination status of heavy metals in sediments, and human health risk associated with fish consumption from western Nigerian offshore in the Gulf of Guinea. Fish stock assessments were carried out across five fishing grounds. Triplicate samples of demersal marine fish species and sediments were collected and analysed for heavy metals (mercury- Hg, cadmium- Cd, lead- Pb and Arsenic- As) by ICP-OES (inductively coupled plasma optical emission spectrometry) using US EPA 200.7 standard method. The geospatial variation of As and Hg revealed that the concentrations were relatively highest at station 1, while Cd and lead Pb concentrations were highest at station 3. Levels of heavy metal in sediment fell below sediment quality guidelines (SQG). While, metal concentrations (As, Cd, Hg and Pb) in demersal marine fish also fell within the permissible levels of FAO/WHO. The ecological indices [Probable contamination index (PCI), mean effect level quotients, newly modified hazard quotient and Hazard quotient (HQ)] indicated low contamination level of heavy metals in sediment. Hazard index (HI) of metals in fish species associated with human health were within recommended threshold of 1 and thus revealed that there would be no significant health risk to the consumers. Percentage of total variance for PC1 is 52.26% whereas PC2 is 27.56% showed weak loading of metals. The study established scientific basis for assessment of metal contamination and risk management of food safety within the western Nigerian offshore waters.

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The study aimed at mapping and characterizing the benthic communities of Lagos Lagoon based on how the sediment define the distribution of organisms in response to dredging activity of the area. The hydrographic survey of was carried out with the aid of an echo-sounder and side-scan sonar and plotted in ArcGIS 10.3.1. The benthic macroinvertebrate ecology in relation to human activities was defined and studied in ten selected dredged stations. Habitat suitability maps of dominant species were plotted using spatial analyst tool. The removal of organisms with the sediment resulted into increased turbidity, suspended solids and modified sediment characteristics in the study area. The known venus, pachymelania, mangrove, estuarine-amphioplus and estuarine-rock macroinvertebrate communities were intact. However, there were changes in the composition of the communities with Donax acutangulus going into extinction. Multivariate analysis showed that the observed benthic communities and sediment characteristics were sandy in nature. The observed assemblage of organism was mostly dominated by bivalve - Atactodea striata of the family Mesodesmatidae at Ogun river station which was characterised by sand. The results revealed a patchy distribution of organisms having abundant macroinvertebrates with less diversity which may be as a result of the on-going dredging activities in the area. Keywords: Macrobenthos, bathymetry, sediment, dredging, GIS