Assessment of heavy metal contamination in seawater, sediments, and fish tissues from Msimbazi Bay, Dar es Salaam, Tanzania.

Heavy metal pollution in marine environments is a growing concern globally due to its potential threats to aquatic ecosystems and human health. Major industrial zones in Tanzania, including Dar es Salaam city, significantly contribute to heavy metal pollution in aquatic ecosystems. The samples for heavy metal analysis in seawater, sediments, and fish tissues were collected, prepared, and digested accordingly, and then analysed using an Atomic Absorption Spectrophotometer. The obtained results showed that marine sediments had higher levels of zinc (105.16 ± 11.83 mg/kg) at the sampling station in the Mangrove creek compared to other sampling stations in the bay, and their concentration levels were found to be in the order of Zn > Pb > Cr > Cd. In the seawater, Pb and Zn were detected within the range considered as natural in the ocean and their concentration were 1.84 and 19.35 µg/l, respectively. The liver of the fish was found to accumulate the highest concentrations of Pb (0.682 ± 0.25) µg g-1 and Cr (0.2 ± 0.09) µg g-1 compared to the kidney, gills, and muscle parts (p > 0.05). Overall, the concentrations in all compartments were below the permissible levels proposed by USEPA, ANZECC and ARMCANZ, FAO and WHO. Despite the study findings on metal levels, there is still a need to implement mechanisms to monitor the contamination of heavy metals in the Msimbazi catchment area and its Bay.