Fluxes of Physicochemical Parameters in The Cross River Estuary, Nigeria

Study on the fluxes of physicochemical parameters and nutrients in the Cross River estuary ecosystem was under taken between June, 2016 and April, 2017. Field data were collected bimonthly at five stations and analysed both insitu and in the laboratory using standard methods. The monthly mean surface water temperature ranged from 26.68±0.74 OC in June 2016 to 33.6±7.84 OC in October 2016, salinity ranged from 0.10±0.12 ‰ in October 2016 to 10.20±2.80 ‰ in March 2017, and DO from 2.740±0.563 mg/l in June 2016 to a maximum of 5.340±2.152 mg/l in January 2017. Values obtained for PO4 , SO4 , NO3 , DO, and BOD in this study were below the permissible limits [1]. There was significant (p < 0.05) temporal variation in all the parameters studied (PO4 , NO3 , SO4 , DO, BOD5 , salinity, temperature and transparency). There was no significant (p > 0.05) spatial variation in PO4 , NO3 , SO4 , temperature and transparency. Parameters studied showed both positive and negative correlations. The implications of these findings are discussed.

Studies on fecundity and spawning of blue crab (Callinectes Amnicola) in Cross River Estuary

Studies on identification of species, fecundity and development stages of blue crab, (Callinectes amnicola) were investigated at the Cross River Estuary between the months of December, 2018 and May, 2019. The parameters used for the study were gonadosomatic and hepatosomatic indices, egg diameter and counts. All measurements followed standard procedures. Gonadosomatic index was at its peak in December (88.9) and April (83.3). This coincided with the peak in egg size suggesting that spawning occurred twice within the period.The low values of hepatosomatic index around December (1.20) and April (0.45) added to confirm the spawning in these months. The species spawns at a mean egg size of 17.55mm. The dimension of crabs examined were in the following range: carapace length 40.0 to 70.0mm, carapace width, 5.0 to 60mm and body weight 40.0 to 140.0g. The relationship between fecundity and weight of crab was significant (r = 0.295: p<0.05), indicating positive correlation. Absolute fecundity of the species ranged between 1,375 and 225,132 eggs. The smallest crab with egg had a carapace width of 39.5mm and weight of 46.9g. Spawning at this size seems to be a strategy adopted by the species to cope with exploitation pressure. The result of this study revealed that C. amnicola had a high reproductive potentials. Hence, adequate regulation is required to enhance sustainability of the species in the Cross River Estuary.

Health risk assessment of heavy metals in Tympanotonus fuscatus along Oron water channel, Cross River Estuary, South Eastern Nigeria

Health risk associated with the consumption of contaminated seafood has become of global concern. The study evaluated potential human health risk associated with heavy metal contamination of Tympanotonus fuscatus along Oron water channel Cross River Estuary. The following metals: chromium (Cr), cadmium (Cd), nickel (Ni), lead (Pb) and zinc (Zn) were analyzed using standard procedure. The target hazard quotient (THQ) and cancer risk (TCR) were estimated using USEPA guidelines. Results showed significant differences (p<0.05) in Ni across the sampling period. The principal component analysis (PCA) had 71.2% of the total variance (with PC 1 represented by Ni and Pb and PC 2 dominated by Cd and Zn). The results for THQ and hazard index (HI) were: Cr = 0.95 mg/kg; Ni = 0.12 mg/kg; Zn = 0.16 mg/kg; Cd = 0.06 mg/kg and Pb = 0.69 mg/kg. These values were below the WHO limit of 1.0 mg/kg. This indicated no adverse health effects associated with the consumption of T. fuscatus from the estuary. A high value of TCR (2.15 x 10-3 mg/kg) was recorded for Ni which showed potential ability to induce moderate cancer risk in human over 70 years of consumption. The health risk associated with accumulated metal in tissues of T. fuscatus underscores the need for periodic biomonitoring of the Cross River Estuary. Keywords: Molluscs, Heavy Metal, Risk assessment, Pollution, Cross River Estuary

Human Health Risk Assessment of Trace Metals in Water from Cross River Estuary, Niger Delta, Nigeria

The aim of this study was to determine the levels of some trace metals in water from Cross River estuary (CRE) and estimate the human health risk associated with water from the estuary via ingestion pathway and dermal contact. The trace metals in water were determined using atomic absorption spectrophotometer and the human health risk assessment of the trace metals was carried out using models stipulated by United States environmental Protection Agency (USEPA). The range for the results in mg/l was as follows: Pb (0.193- 0.632), Cd (0.118 - 1.084), Ni (0.048 -0.632), Fe (0.056 - 0.921), Zn ( 0.063 - 0.242), Cu(0.072 - 0.146). All the investigated metals were above the WHO limit except zinc and copper. The target hazard quotient (THQ) via ingestion pathway for Pb, Cd and Ni were higher than unity. Also, the hazard indices for all the investigated metals in all the study sites were higher than unity. The target hazard quotient and Hazard index via dermal pathway were less than one for all the metal investigated, except Cd at Ebughu. Regular monitoring and minimization of anthropogenic activities resulting in elevated metal concentration is recommended.