Bioaccumulation dynamics, noncarcinogenic and carcinogenic risks of heavy metals in commercially valuable shellfish and finfish species from the world largest floating slum, Makoko, Nigeria.

This study examined ten heavy metals in five species: Macrobrachium vollenhovenii, Penaeus monodon, P. notialis, Chloroscombrus chrysurus, and Pseudotolithus typus, from Makoko floating slum, Lagos Lagoon to discern their bioaccumulation potentials, sources of origin, and health implications. The concentrations were in this order: Fe (4.172-10.176) > Zn (1.310-5.754) > Mn (0.475-2.330) > Cu (0.238-1.735) > Pb (0.121-0.391) > Cd (0.055-0.283) > Co (0.056-0.144) > Ni (0.039-0.121) > Cr (0.022-0.095) > As (0.003-0.031) mg/kg. The MPDI denotes "low toxicity," and the BAF/BSAF revealed that benthic species had higher bioconcentration potentials. Multivariate analyses revealed that heavy metals exhibited mutual relationships during chemical transport, and their sources were both geogenic and human-induced. The HI values were below 1, and the TCR values were below the threshold of 1 × 10-4. This suggests that the probabilities of noncancer and carcinogenic risks in human populations due to long-term consumption of the evaluated species are unlikely.

Polycyclic aromatic hydrocarbons distribution in fish tissues and human health risk assessment on consumption of four fish species collected from Lagos Lagoon, Nigeria.

Lagos Lagoon is a very popular lagoon in Lagos state that receives effluents from neighboring industries. These effluents tend to increase the level of contaminants in the lagoon, thereby creating more stressors for aquatic animals. Determination of polycyclic aromatic hydrocarbons (PAHs) in four commonly consumed fish species from the lagoon and the prediction of possible health risks associated with their consumption were performed in this study. Various levels of PAH were detected in the fish tissues with the highest total concentration of PAH in Sarothoredon melanotheron. High concentrations of benzo(a)pyrene were noticed in Sarothoredon melanotheron and Ethmalosa fimbriata, and their values were above the guideline value of 0.002 µg/g. The dietary daily intake (DDI) value in S. melanotheron 82.00 ×10-5 µg/g/day was highest. Carcinogenic toxic equivalents (TEQ) showed that consumption of S. melanotheron had higher potential to pose carcinogenic risks, while the excess cancer risk (ECR) index for the PAHs in all the assessed fish species was beyond threshold values indicating potential carcinogenic risk from their consumption. No significant association was found between the concentration of PAHs and the size of the fish. Target hazard quotient (THQ) results suggested absence of potential non-carcinogenic risk if individual PAH in the fish are consumed frequently. The study however established possible carcinogenic human health risk from consumption of the fish obtained from Lagos Lagoon. The study recommends monitoring of contamination and consumption of fish from harvest sites within the study region.

Microplastics in carnivorous fish species, water and sediments of a coastal urban lagoon in Nigeria.

Plastic marine debris is a common source of pollution. Recent research has shown that plastic debris has a negative impact on marine organisms and the environment. For the first time, we investigated the presence of microplastics (MPs) in the Nigerian Lagos Lagoon ecosystem water, sediment, and the most important fish species (Hepsetus odoe, Chrysichthys nigrodigitatus, Oreochromis niloticus, and Lachnolaimus maximus). MPs were found in water, sediment, and three carnivorous fish species (H. odoe, C. nigrodigitatus, and L. maximus), except for herbivorous O. niloticus, raising concerns about the health of the Nigerian Lagos Lagoon ecosystem and the human food chain. Across the lagoon, fibres were more concentrated in the water, while fragments predominated in the sediment. Plastic debris from recreational, industrial, and domestic wastes contributed significantly to this contamination. Given the potential dangers of MPs to human health, it is critical to protect the ecosystem and its inhabitants in the Lagoon from plastic pollution. Our findings highlight the need for urgent measures to protect Nigeria's fragile coastal and marine ecosystems.

Dataset on microplastics and associated trace metals and phthalate esters in sandy beaches of tropical Atlantic ecosystems, Nigeria.

This article presents data on the occurrence and distribution of phthalate esters and metals associated with microplastics (MPs) (1-5 mm) collected from four beaches in the tropical Atlantic ecosystems, Nigeria, Gulf of Guinea. Information on microplastics extraction by density flotation with saturated NaCl and polymer identification with attenuated total reflectance infra-red spectroscopy (ATR-FTIR) is also provided. Analysis of six phthalate esters (PAEs) (dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DnBP), benzyl butyl phthalate (BBP), di (ethyl hexyl) phthalate (DEHP), and di n-octyl phthalate (DnOP)) associated with the microplastics by performed using Gas chromatography-mass spectroscopy (GC-MS). Metals including Ag, Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Pb, Sb, Se, Si, Sr, Ti, Tl, V, and Zn were analysed by inductively coupled plasma-optical emission spectrometry (ICP-OES). The data present the separation of microplastics from sediment, extraction with cyclohexane/ethyl acetate (1:1, v/v) and 10% HNO3 for phthalate esters and metals, respectively, and the determination of target analytes concentrations. The compositional distributions of MPs and levels of carcinogenic and toxic metals and phthalate esters are presented. The dataset could be used for the evaluation of ecological risk associated with PAEs in the marine ecosystems.

Sawmill Activities Near the Lagos Lagoon, Nigeria: Polycyclic Aromatic Hydrocarbons and Embryotoxic Evaluations of Sediment Extracts Using Clarias gariepinus.

The physicochemical parameters and 16 priority PAHs in surface water, porewater and sediment at a sawmill wastes-impacted and High-Rise study sites on the Lagos lagoon in Nigeria were assessed. Further, the embryotoxic effects of sediment organic and porewater extracts from the study sites were evaluated in Clarias gariepinus (African sharptooth catfish) embryos for 26 h. High molecular weight PAHs dominated the PAHs profile especially in the sediment. Source apportionment of the PAHs in the three environmental matrices revealed mainly pyrogenic sources. Developmental abnormalities and decreased hatching success were observed in C. gariepinus embryos exposed to extracts from the Okobaba site compared to High-Rise study site. The results demonstrate the potential though non-significant ecological risk of sawmill activities near the lagoon on water quality and fisheries. Further studies are recommended to provide holistic evidence-based information to promote sustainable fisheries in the lagoon in support of the UN SDGs 13 (climate action) and 14 (life below water).

The intersex phenomenon in Sarotherodon melanotheron from Lagos lagoon (Nigeria): Occurrence and severity in relation to contaminants burden in sediment.

The correlation between endocrine active contaminants in the environment and alterations in reproductive development of Sarotherodon melanotheron from Lagos lagoon has been investigated. Sediment and a total of 155 fish (74 males and 81 females) were collected between November 2014-March 2015 from selected contaminated sites (Ikorodu, Oworonshoki, Makoko and Idumota) and a putative control site (Igbore) along the lagoon. Sediment contaminant analysis revealed, significantly higher concentration of lindane, dieldrin, 4-iso-nonylphenol, 4-t-octylphenol and monobutyltin cation at the contaminated sites. Examination of gross morphological and histological changes of fish gonads showed a 27.4% prevalence of intersex in the sampled fish, of which 78% were males (testes-ova) and 22% were females (ovo-testis). Quantitative PCR (qPCR) of liver transcripts revealed the presence of vitellogenin (vtg) levels in male fish from contaminated sites. Zona radiata proteins (zrp) mRNA levels were significantly higher in females, compared to male fish. In general, significantly lower vtg and zrp transcripts levels were recorded at Igbore (control site), compared with contaminated sites. Principal component analysis (PCA) showed site and sex relationship in biological responses and contaminants, including trace metals, demonstrating that measured endocrine responses in fish were associated with contaminant burden in sediment. In addition, positive relationships were observed in male fish from Idumota, Oworonshoki and Ikorodu with vtg and dieldrin/4-iso-nonyphenol, with higher levels in male fish, compared to females. Further, contaminants from the Makoko, Oworonshoki and Ikorodu sites were positively associated with higher GSI and zrp in females. More importantly, the severity of intersex and changes in vtg transcripts imply a progressive feminization of male fish with concomitant alteration in the reproductive health of fish inhabiting the Lagos lagoon.

Structural dynamics of microbial communities in polycyclic aromatic hydrocarbon-contaminated tropical estuarine sediments undergoing simulated aerobic biotreatment.

Coastal sediments contaminated by polycyclic aromatic hydrocarbons (PAHs) can be candidates for remediation via an approach like land farming. Land farming converts naturally anaerobic sediments to aerobic environments, and the response of microbial communities, in terms of community structure alterations and corresponding effects on biodegradative activities, is unknown. A key goal of this study was to determine if different sediments exhibited common patterns in microbial community responses that might serve as indicators of PAH biodegradation. Sediments from three stations in the Lagos Lagoon (Nigeria) were used in microcosms, which were spiked with a mixture of four PAH, then examined for PAH biodegradation and for shifts in microbial community structure by analysis of diversity in PAH degradation genes and Illumina sequencing of 16S rRNA genes. PAH biodegradation was similar in all sediments, yet each exhibited unique microbiological responses and there were no microbial indicators of PAH bioremediation common to all sediments.

Metal uptake, oxidative stress and histopathological alterations in gills and hepatopancreas of Callinectes amnicola exposed to industrial effluent.

Metal uptake by biota due to elevated environmental concentrations elicits oxidative stress and could lead to pathological outcomes. The relationship between the histopathological profile of hepatopancreas and gills and altered biochemical features (antioxidant enzymes i.e. GSH, GPx, CAT, SOD, lipid peroxidation (MDA) and serum protein) in the blue crab, Callinectes amnicola from contaminated parts of the Lagos Lagoon was investigated. Monthly crab, sediment and surface water samples were taken from effluent receiving areas of the Lagos lagoon i.e. Makoko, Okobaba, Iddo, Ikoyi and Mid-lagoon (control site) over an 18-month period and analyzed for metal levels (Pb, Cd, Zn and Cu). Significantly higher levels of GPx and lower levels of Pb, Zn and Cu was recorded in gills and hepatopancreas of crabs from the mid-lagoon compared to crabs from other sites. Reaction patterns of gills across the different sites of the lagoon included regressive (ranging from epithelial lifting, disruption of pilaster cells, detached cuticle to focal necrosis) and circulatory disruptions (oedema); increased activity of GSH and GPx in gills were positively correlated with lesions of lower importance factor. Reaction patterns in hepatopancreas were more regressive including vacuolation/infiltration of fatty lobules, necrosis, granuloma, disintegrated lumen, atrophied tubules and loss of lobular hepatocyte structure; increased activity of GSH, GPx and CAT were positively correlated with lesions of low importance factor in the hepatopancreas. Findings show that lesions in both gills and hepatopancreas of the blue crab could be associated with uptake of metals, depleted antioxidant activity and incidence of lipid peroxidation in tissue.

Concentration and Human Health Implications of Trace Metals in Fish of Economic Importance in Lagos Lagoon, Nigeria.

BACKGROUND: The most significant sources of food-borne diseases are microbiological and chemical hazards. The health risk due to consumption of food from aquatic ecosystems contaminated with hazardous chemicals including metals has increased globally, especially in developing countries like Nigeria. OBJECTIVES: The concentration and human health implications of trace metals in fish of economic importance in Lagos lagoon were investigated by determining the degree of contamination with heavy metals of selected fish from Lagos lagoon and assessing the possible health risks associated with fish consumption. METHODS: Fish of economic importance including Caranx hippos, Chrysichthys nigrodigitatus, Elops lacerta, Galeoides decadactylus, Ilisha africana, Liza falcipinnis, Lutjanus goreensis, Mugil cephalus, Pseudotolithus senegalensis, Sarotherodon spp, Sphyraena spp, and Tilapia spp were bought from fishermen fishing in Lagos lagoon. The fish tissue samples were digested and analyzed in five replicates for heavy metals (lead, cadmium, iron, manganese and zinc) using a Varian AA600 atomic absorption spectrometer. RESULTS: There were considerable variations in the concentrations of heavy metals among different species. The twelve fish species collected from Lagos lagoon were found to contain various concentrations of heavy metals and the levels of accumulation of these heavy metals varied across different species. Lead, cadmium, and manganese were present in all the studied fish species at higher concentrations than the maximum allowable concentrations in fish recommended by the Food and Agricultural Organization (FAO) and World Health Organization (WHO). The target hazard quotient (THQ) estimated for individual heavy metals through consumption of different fish species was less than 1 for all individual heavy metal in all the fish species. CONCLUSIONS: Controls on the dumping of wastes in the lagoon are needed, along with regular monitoring. Currently, no potential non-carcinogenic health risks from ingestion of a single heavy metal through consumption of these fish species was found.

Occurrence and distribution of monocyclic aromatic hydrocarbons (BTEX) and the impact on macrobenthic community structure in Lagos lagoon, Nigeria.

The widespread distribution of petroleum products arising from the rapid growth of the petroleum industry in Nigeria has resulted in the pollution of the environment through oil spills involving leakages from tankers, pipelines, tank farms, and dumping of waste petroleum products. The impacts and distribution of major toxic components (benzene, toluene, ethylbenzene, and xylene (BTEX)) of petroleum products in water and sediment samples collected from sampling stations in the Lagos lagoon was investigated over a 2-year period (February 2009-July 2010). The distribution of benthic communities in the different sampling stations of the Lagos lagoon was assessed. The determination of hydrocarbon levels in the samples showed that the levels of total hydrocarbon content (THC) in the water samples around the Atlas Cove and Apapa were high with values ranging from 2.03 to 31.38 mg/l and 4.04 to 22.89 mg/l, respectively. The highest value of total BTEX in the lagoon sediment was also recorded in the Apapa station (450.53 µg/kg), where oil depots and tank farm facilities are located. The study of the macrobenthic community structure showed that the species richness ranged from 1.57 to 2.02 in the reference station, Unilag, while in the Atlas Cove, Iddo, and Apapa stations, it ranged from 1.80 to 2.89, 1.95 to 3.03, and 1.86 to 2.95, respectively. The highest number of organisms (183) was recorded in the reference stations, while the least number (46) was recorded in Apapa. The main hydrocarbon pollution indicator species identified in the impacted aquatic stations were Nais eliguis and Heteromastus filiformis. The levels of hydrocarbon observed in the aquatic environment showed that there is widespread contamination as a result of petroleum product importation, storage, and distribution. The assessment of the monocyclic aromatic hydrocarbon and benthic community will therefore provide important tools for early detection, diagnosis, and management of hydrocarbon pollution in the Lagos lagoon.

Microbial Communities in Sediments of Lagos Lagoon, Nigeria: Elucidation of Community Structure and Potential Impacts of Contamination by Municipal and Industrial Wastes.

Estuarine sediments are significant repositories of anthropogenic contaminants, and thus knowledge of the impacts of pollution upon microbial communities in these environments is important to understand potential effects on estuaries as a whole. The Lagos lagoon (Nigeria) is one of Africa's largest estuarine ecosystems, and is impacted by hydrocarbon pollutants and other industrial and municipal wastes. The goal of this study was to elucidate microbial community structure in Lagos lagoon sediments to identify groups that may be adversely affected by pollution, and those that may serve as degraders of environmental contaminants, especially polycyclic aromatic hydrocarbons (PAHs). Sediment samples were collected from sites that ranged in types and levels of anthropogenic impacts. The sediments were characterized for a range of physicochemical properties, and microbial community structure was determined by Illumina sequencing of the 16S rRNA genes. Microbial diversity (species richness and evenness) in the Apapa and Eledu sediments was reduced compared to that of the Ofin site, and communities of both of the former two were dominated by a single operational taxonomic unit (OTU) assigned to the family Helicobacteraceae (Epsilonproteobacteria). In the Ofin community, Epsilonproteobacteria were minor constituents, while the major groups were Cyanobacteria, Bacteroidetes, and Firmicutes, which were all minor in the Apapa and Eledu sediments. Sediment oxygen demand (SOD), a broad indicator of contamination, was identified by multivariate analyses as strongly correlated with variation in alpha diversity. Environmental variables that explained beta diversity patterns included SOD, as well as levels of naphthalene, acenaphthylene, cobalt, cadmium, total organic matter, or nitrate. Of 582 OTU identified, abundance of 167 was significantly correlated (false discovery rate q≤ 0.05) to environmental variables. The largest group of OTU correlated with PAH levels were PAH/hydrocarbon-degrading genera of the Oceanospirillales order (Gammaproteobacteria), which were most abundant in the hydrocarbon-contaminated Apapa sediment. Similar Oceanospirillales taxa are responsive to marine oil spills and thus may present a unifying theme in marine microbiology as bacteria adapted for degradation of high hydrocarbon loads, and may represent a potential means for intrinsic remediation in the case of the Lagos lagoon sediments.

Lagos lagoon sediment organic extracts and polycyclic aromatic hydrocarbons induce embryotoxic, teratogenic and genotoxic effects in Danio rerio (zebrafish) embryos.

An expansion of anthropogenic activity around Lagos lagoon, Nigeria, has raised concerns over increasing contaminants entering the lagoon's ecosystem. The embryotoxicity, teratogenicity and genotoxicity of sediment organic extracts from four sampling zones around Lagos lagoon, Ilaje, Iddo, Atlas Cove and Apapa, as well as the dominant polycyclic aromatic hydrocarbons (PAHs) identified in water measured during the wet season (naphthalene, phenanthrene, pyrene, benzo[a]pyrene and a mixture of these), were assessed with Danio rerio embryos. Embryos were exposed to varying concentrations of toxicants from 0-72 h post-fertilization (hpf). Embryotoxicity at 72 hpf showed a dose-dependent increase in mortality upon exposure to extracts from all zones, except Atlas Cove. Similarly, higher levels of teratogenic effects, such as increased oedema, and haemorrhage and developmental abnormalities resulted from exposure to extracts from Ilaje, Iddo and Apapa zones. Treatment with single PAHs revealed that significant levels of detrimental effects were obtained only for phenanthrene. The modified comet assay revealed that the oxidative damage to DNA was generally low (<12 %) overall for all sediment extracts, but was significantly elevated with Ilaje and Iddo sediment extracts when compared with solvent controls. Oxidative damage was observed with the single PAHs, phenanthrene and benzo[a]pyrene, as well as with the PAH mixture. This study highlights that Lagos lagoon sediment extracts have teratogenic, embryotoxic and genotoxic properties, which are likely due to the high molecular weight PAHs present in the extracts, some of which are known or are suspected human carcinogens.