Metal bioaccumulation and energy biomarkers in tissues of two populations of Chiromantes eulimene from Richards Bay Harbour, South Africa

• Main Authors: Ntando Majola, Hendrick Mduduzi Mzimela, Joshua Idowu Izegaegbe
• Format: Article
• Language: English
• Published: Elsevier 2020-11-01
• Series: Scientific African
• Subjects: Metal; Carbohydrate; Lipid; Protein; Biomarker; Crab
• Online Access: http://www.sciencedirect.com/science/article/pii/S2468227620302969

There is a growing concern about the level of contamination from industrial mining and other human activities that have taken place for over four decades in the Richards Bay area. A study was undertaken to assess the level of metal contamination through bioaccumulation and biological responses of mud crab species Chiromantes eulimene. Metals from the water, sediment and different tissues of two populations of crabs from Bhizolo Canal and Mhlathuze Estuary were analysed and compared. Water and sediment samples were digested with nitric acid and crab tissues with nitric acid and hydrogen peroxide using hot plates. Metal concentrations in water, sediment and crab tissues were analysed using the ICP-OES. High concentrations of metals were observed in the gills and digestive glands of crabs from Mhlathuze Estuary compared to other tissues, with high concentrations of Ag, Cr, Cd, Co and Zn in the gills and Al, Ni, Fe, Mn and Pb in the digestive glands. Bhizolo Canal also showed high concentration of metals in the gills except for Mn, Al and Cu. The gills and digestive glands are metabolically active tissues and metal accumulation tend to occur on such tissues, also, the digestive gland have high metallothioneins thus sequestering metals. In water, only Ag, Mn and Ni were higher in Mhlathuze Estuary and the rest of the metals were higher in Bhizolo Canal with only Cd, Cr, Co, Cu and Zn showing significant differences (p<0.05). Bhizolo Canal also showed high concentration of metals in sediment compared to Mhlathuze Estuary but only Co and Zn were significantly different. High metal levels in Bhizolo Canal may be associated with adjacent industrial activities such as the aluminium smelter and Phosphoric Acid Company. Statistically higher concentration of carbohydrates and protein in crabs from Bhizolo Canal may represent a response to stress to meet energy demand while significantly higher lipid content in the gills of crabs from Mhlathuze Estuary indicated improved energy storage. This study managed to link pollution to industrial activities in Bhizolo Canal and to mining and sewage in Mhlathuze Estuary.