Tag Archives: biomonitoring


The aim of this study was to assess human and ecological risk posed by water and sediment quality of New Calabar New (NCR) using Chrysicthys Nigrodigitatus. For this study, chemical- and bio-monitoring assessments were carried out in three sampling stations (Choba, Ogbogoro and Iwofe) of NCR. A Fish Consumption Survey (FCS) was also implemented to assess the risk of exposure of subsistence fishers from host communities of the sampling stations of NCR. Using data from FCS, mathematical models were used to charactconsumptionerize risk due to the consumption of fish. Chemical monitoring involved the assessment of pysico-chemical variables of water with an evaluation ofEnvironmental Water Quality Index (EWQI) and sediment quality. Biomonitoring involved the assessment of the edible part of fish tissue (skin and muscle) for chemicals of potential concern (COPC). Physico-chemical water analysis and set against SON benchmarks, results showed that temperature, pH, conductivity and dissolved oxygen values were abnormal, while heavy metals and PAH were normal. The evaluated EWQI was marginal for NCR. Sediment quality showed slightly elevated PAH level at Ogbogoro station while heavy metals remain normal. Fish edibility study set against RfD benchmarks of USEPA, indicated a slightly elevated PAH, hence fish from NCR was unsafe for consumption. The FCS showed that an average of 1.2kg/day/ of C. Nigrodigitatus was consumed by respondent from NCR basin, with an age group range of 18-34 forming the highest consumers. HQ<1 for COPC, meaning their levels in the edible part of tissue are not acutely hazardous on consumption, but PAH, a carcinogenicchemicalforming part of the assessed COPC, showed a carcinogenic risk characterization of 1.4E-04, 1.3E-04 and 1.3E-04 respectively for subsistent fishers from Choba, Ogbogoro and Iwofe.

Keywords: Fish Consumption Survey, Integrated Risk Assessment, Water Quality Index, biomonitoring


The aim of this study was to evaluate the impact of environmental contaminants on gross anatomy (external and internal) and histopathologic biomarkers in liver, kidney and gills of African Silver Catfish (Chrysichthys Nigrodigitatus) collected from New Calabar River (NCR) in comparison to a reference site (African Aquaculture Centre, ARAC). NCR was chosen for this study because of its reported elevated levels of toxicants. For this study, chemical monitoring and bio-monitoring assessments were carried out in three sampling stations (Choba, Ogbogoro and Iwofe) of NCR. The chemical assessment involved EWQI assessment, sediment quality analysis, and heavy metals and PAH assessment. The histological bio-monitoring assessment involves the sampling of twenty table-sized fish harvested from the wild – the Choba station of NCR, which were compared with ten table-sized fishes of the same specie harvested from an aqua-cultured centre, ARAC, which has a controlled water quality system. EWQI was marginal, Sediment analysis showed slightly elevated level of PAH, Fish health Assessment Index (HAI) and fish biometric (CF) were worse in fishes harvested from NCR. Histopathological assessment was done in a qualitative and semi-quantitative scenario and fishes from NCR shows worse results as compared to those from ARAC. The qualitative assessment of target organs show alterations of target, which includes: Neurotic foci, vacuolation, melano-macrophageal centre and fatty changes in liver; intercellular haemorrage, intestinal oedema and melano-macrophageal centre in kidney and; telangiecstasia, epithelial lifting and hyperplasia in gills. Semi-quantitative histological assessment showed that NCR and ARAC had fish index values of 31.1 and 3.6 respectively. Following Man Whitney Test statistical analysis, significant differences (p<0.05) were noted between NCR and ARAC.

Keywords: Ecotoxicology, Histology, biomarker, biomonitoring