Spectroscopic investigation of heavy metals Bioaccumulation in marine mollusc species at Tudor creek, Mombasa Kenya
Swaleh, Mariam M.
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Mombasa is a coastal city that has undergone rapid urbanization leading to pollution of the marine environment. The major sources of pollution in Mombasa are solid waste and waste water from industries, domestic sewage and storm water runoff. Marine mollusks are good biomonitoring organisms of heavy metals pollution in the environment. They can bioaccumulate high concentration levels of heavy metals in their surrounding environment without death. Bioaccumulation of heavy metals in marine mollusks therefore, can depict the extent of pollution in a given area. This study therefore aimed at investigating heavy metals bioaccumulation on selected marine molluscs of genus (saccostrea cucullata) oysters, (Acanthopleura gemmata) chitons, (Mytilus edulis) mussels and donax at Tudor creek. An atomic absorption spectrometer was used in this study to determine the concentration levels of heavy metals in the organisms’ flesh and shell samples as well as water, sediment, rocks and macro algae samples. The metals analyzed included: Fe, Cu, Zn, Mn, Pb, Cd and Cr. Concentration of metals varied with location, genus, size, tissue and shells of the mollusks. The results showed that of all the metals analyzed Fe was the most abundant heavy metal in most of the samples analysed. Pb and Cd were detected in the shell samples but occurred in levels below the detection limit in the flesh samples of all molluscs except chitons and oysters samples. chitons had the highest concentration of Fe (3182.01±41.31 μg/g) while mussels had the highest concentration of Zn (2504.92±6.96 μg/g) overall. The range of metals concentration in all the species was as follows: Fe: 9.31±3.06 μg/g to 3182.01±41.30 μg/g, Zn: Nd to 2504.92±6.96 μg/g, Cu: 2.90±0.48μg/g to 254.98±9.50 μg/g, Mn: Nd to 25.71±5.72 μg/g, Pb: Nd to 70.35±2.47 μg/g, Cd: Nd to 13.92±1.25 μg/g and Cr: Nd to 98.24±19.73 μg/g. The sediment samples had a high concentration of heavy metals compared to the water samples. Fort Jesus had the highest concentration of Pb (38.25±2.28 μg/g), Cr (4.61±1.34 μg/g), Fe (1174.48 ±9.52 μg/g), and Zn (34.19±3.31 μg/g), while Coast General Hospital had highest concentration of Cu (4.61±1.34 μg/g) and Mn (10.95±0.59 μg/g). The marine algae species U. lactuca and U. reticulata had high concentration levels of Fe 376.77±32.56 μg/g and 49.91±19.78 μg/g respectively while Cd was not detected. U. lactuca was a better accumulator of most metals as compared to U. reticulata. Fe (336.64±25.79 μg/g) had the highest concentration in rock samples compared to the other metals while Pb and Cd were not detected in rock samples. The results suggested that chitons are good accumulators of Fe and Mn, mussels are good accumulators of Zn and Cr whereas oysters accumulate Cd, Cu and Pb. It was concluded that bioaccumulation of heavy metals varied with location, species type, body part and size of molluscs. It was further concluded that the marine molluscs were better accumulators of heavy metals than water, sediment and rocks samples.