The occurrence of metals viz., lead (Pb), zinc (Zn), copper (Cu), iron (Fe), cadmium (Cd) and chromium (Cr) in water and fish ( Chrysichthys nigrodigitatus) samples collected bi-monthly from nine stations (water) and 3 designated landing sites (fish) of Badagry creek were investigated using atomic absorption spectrophotometer (AAS) method. With an exception of cadmium, metals concentration was lower in the water samples and higher in the fish tissues, indicating a bioaccumulation tendency of fish. Concentration levels in water were found in decreasing order of magnitude Cr > Pb > Fe > Zn > Cu > Cd. However, metals investigated except Cu (highest concentration in the liver) had highest concentrations in the fish gills, which could be related to the uptake pathway. The relatively lower wet season Cu, Pb, Cr and Cd in water could be attributed to a dilution effect of rainfall. Although, presently the mean concentrations of all the heavy metals except Pb in this study were moderate and within the Federal Environmental Protection Agency (FEPA) permissible standard limit for aquatic life , the elevation of metal concentrations in this creek is inevitable under the prevailing conditions of increasing urbanization, industrialization and other forms of modernization in Badagry and environs. Nevertheless, it is imperative to ensure regular monitoring of heavy metal loading in this creek and other water bodies with a view to safeguard public health.
In order to assess the zooplankton community in an anthropogenic-disturbance Badagry creek, Zooplankton and water samples were collected and analyzed bi-monthly from November 2011 to September 2013 in nine stations representing its three different zones using standard methods. Zooplankton was identified to species-level using relevant texts and counted under a Microstar IV Carl Zeiss binocular microscope calibrated at different magnifications. Diversity was determined using Shannon-Weiner (H), Simpson (1-D) and Evenness (e^H/S) indices. Water samples were analysed for temperature, pH, salinity, conductivity, turbidity, dissolved oxygen, water depth and nitrate. Data were analysed using descriptive statistics, ANOVA, cluster and Canonical correspondence analysis (CCA) at α = 0.05. A total of 56 species comprising 26 species of rotifers, 15 species of arthropoda, 4 species of ciliophora, 3 species of cnidaria, and 2 species of ctenophora, foraminifera, mollusca, protozoa each, with an array of meroplankton / juvenile stages of the order copepod of subphylum crustacea were recorded. Diversity indices were highest (H = 2.20; 1-D = 0.80; e^H/S = 0.27) at station 6 and lowest in station 8 (H = 1.20; 1-D = 0.56) and station 1(e^H/S = 0.14). Salinity/conductivity, nitrate and water depth were significantly different (p < 0.05) among the study stations. CCA revealed salinity/conductivity and nitrate were the most important abiotic factors co-related with the zooplankton abundance in Badagry creek. The moderately low zooplankton communities’ diversity and abundance in Badagry creek point at different natural and anthropogenic factor impacts.
This study aims to examine trace metals (Pb, Cd, Cr, Zn, and Cu) concentration in muscle tissues of four fish species from Five Cowries Creek and assess the safety risks posed by consuming these fish species. For this purpose, fish species such as Cynoglossus senegalensis, Mugil cephalus, Chrysichthys nigrodigitatus and Pseudotolithus typus were procured monthly from anglers in Five Cowries Creek, Lagos, from February to May, 2019. The fish muscle tissues were digested according to the international standards, and the trace metals were measured using an atomic absorption spectrophotometer (AAS). Results revealed that the ranking order of trace element concentrations followed this sequence: Pb > Cr > Zn > Cu > Cd. There were significant differences (P < 0.05) in Pb and Cr among the fish species. Consumer health risk was evaluated using non-carcinogenic and carcinogenic risk indices. The results showed that EDI and target hazard quotient (THQ) of Cr, Zn, Cu and Cd suggested that fish species consumption did not pose risk to consumer health. Nevertheless, the estimated daily intake (EDI) along with THQ of Pb indicated potential health risks to consumers (children and adult) of Chrysichthys nigrodigitatus. The target hazard index (THI) of trace elements in all investigated fish species exceeded the guideline value of 1, indicating an adverse health risk for exposed consumers. However, the carcinogenic risk of Pb was negligible for children and adult consumers of fish species. The results are anticipated to create alertness among the public on the safety risks as a result of consuming metal-contaminated fish. Authorised regulatory agencies should control the unregulated uses of Five Cowries Creek, Lagos and associated water bodies through the enforcement of various regulations, policies and laws.
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