Assessment of Heavy Metal Pollution in Octopus cyanea in the Coastal Waters of Tanzania

Background. The accumulation of toxic metals in marine environments has become a problem of increasing concern. In Tanzania, large amounts of industrial and domestic waste from major coastal cities such as Dar es Salaam, Tanga and Zanzibar are released into the marine environment without undergoing treatment. The wastes are sometimes contaminated with hazardous heavy metals such as lead, zinc and cadmium, among others. Elevated concentrations of these metals have been measured in sediment along the coastal waters of Tanzania. These metals have effects on both aquatic organisms and humans through consumption of contaminated fish and other aquatic foods. Despite the social-economic support provided by marine biota, there is no information on the levels and magnitude of octopus contamination by heavy metals or their safety for human consumption. Objective. Investigate the spatial concentrations of lead in the muscle tissue and liver of O. cyanea and sediment in the coastal waters off Dar es Salaam and Tanga, Tanzania. Methods. Concentrations of lead, from samples of O. cyanea muscle and liver tissue and sediment, were determined using inductively coupled plasma atomic emission spectroscopy (ICP-AES). Results. The concentration of lead in the muscles and liver of O. cyanea ranged from 0.01 to 21.6±2.41 μg/g. On the other hand, the concentration of lead in sediment ranged from 6.33±0.39 to 13.85±3.31 μg/g. Discussion. Levels of lead were detected in the muscle and liver tissues of the O. cyanea, but presumably, below toxic risk if provisional tolerable weekly intake (PTWI) levels are considered. However, the present results should be taken as worrisome in view of health implications for populations that depend on octopus as a source of protein. Sediment samples were below both Florida’s ‘No effect level’ and the threshold value of Environment Canada. Competing Interests. The authors declare no competing financial interests.