Concentration and Biomagnification of Heavy Metals in Biota of the Coastal Marine Areas of Tanzania

Abstract

Abstract:The concentrations of heavy metals (As, Hg, Cr, Pb and Zn) were measured in the macroalgae, macrobenthos and fish from the Tanzanian coastal marine environment in order to ascertain the biomagnification using stable isotopes of C and N. Macroalgae samples from the central marine areas of the Tanzanian coast had higher mean concentrations of Hg (0.17 ± 0.01 µg/g) and Cr (23.7 ± 4.15 µg/g) compared to other locations. Higher concentration of Hg (0.06 ± 0.02 µg/g) was detected in the Ulva fasciata close to the Msimbazi Creek in Dar es Salaam, whereas the highest concentration of Cr (45.5 ± 6.83 µg/g) was found in Ulva petrusa near Dar es Salaam port. The crab Portunus pelagicus collected from Pangani river estuary contained 411.5 ± 13.04 µg/g of Zn. The other metals were uniformly distributed in macrobenthos from the entire coast. Mercury and lead in the biota were found to biomagnify along the Arius dussumieri and Lethrinus lentjan food chains as suggested by the significant positive relationships between log-pollutant concentrations in fish muscle tissues vs. δ 15 N signatures. Zinc in muscle tissues was found to be transferred along the food webs although no biomagnification was observed. Arsenic and chromium were found to decrease with the rise of the trophic position. Metal concentrations in macroalgae, macrobenthos and fish were compared with quality guidelines values by FAO (Food and Agricultural Organization) in 1983 and they all were below permissible limits for human consumption.

Lead and Cadmium Levels in Water, Surficial Sediments, and Edible Biota of Urban Rivers in Dar es Salaam, Tanzania, During Two Seasons

“…The Cd and Pb contamination levels at Kz 1 and Ms 4 indicate that the two locations can be considered hotspots. Generally, the Pb and Cd levels observed in sediment in the area are similar to those recorded in other locations on the Tanzanian coast, particularly those that are relatively less anthropogenically influenced [20][21][22]49]. The apparent variance can be attributed to the differences in the characteristics of the specific study locations, periods, and analytical methods used; some researchers analyzed the metals in the bulk samples, while others, such as Bungala et al [22], Ngassapa et al [50], and Sawe et al [51], used metal speciation.…”

“…Metal pollution in aquatic environments is a well-researched field in Tanzania, although many locations remain to be investigated. Over a period of more than two decades, authors have used various environmental and biological matrices, including sediments, water, soil, plants, and biota, to measure concentrations of metals in various locations in the country [17][18][19][20][21][22]. Because of their toxicity, persistence, and non-degradability, the elements Pb, copper (Cu), Cd, chromium (Cr), mercury (Hg), arsenic (As), cobalt (Co), nickel (Ni), and zinc (Zn) were the most commonly researched.…”

Trophic dynamics of methylmercury and trace elements in a remote Amazonian Lake

“…Barwick and Maher (2003) highlight that there still are many gaps on the comprehension of trace element trophodynamics in aquatic food webs. Although Hg biomagnification has been consistently demonstrated in different ecosystems, for other elements (e.g., Cd and silver -Ag) the occurrence of trophic magnification depends on the ecosystem investigated, as well on the toxicokinetic of the chemical species of the studied elements, among other factors (Lavoie et al 2013;Bungala et al 2017;Liu et al 2019). Zinc constitutes a good example of contrasting scenarios for the same element.…”

“…Mercury biomagnification is related to its organic form (Lavoie et al 2013), subsequently to the methylation process and methylmercury (MeHg) synthesis (Coelho-Souza et al 2011). On the other hand, elements such as nickel (Ni) tend to undergo trophic dilution (concentrations decrease upwards the trophic web, i.e., the top predator species present the lowest ones) in aquatic ecosystems (Nfon et al 2009;Pereira et al 2010;Guo et al 2016;Monferrán et al 2016;Bungala et al 2017).…”

Heavy metals and pesticide residues as quality determinants for sustainable management of prawns along the Indian coastline of Tanzania

“…Furthermore, Pb, As, Cd, Fe and Cu were detected in Fenneropenaeus indicus in Dar es Salaam City with concentration range of 1.173 -2.325 mg/kg (Saria, 2016). In addition, As, Hg, Cr, Pb and Zn were also detected in fish from the Tanzanian coastal areas with higher mean concentrations of Hg (0.170.01 mg/kg) and Cr (23.70 mg/kg) (Bungala, Machiwa & Shilla, 2017). Similarly, high concentrations of Hg (0.06 mg/kg) were detected in fish from the Msimbazi Creek, Dar es Salaam and Cr (45.5 mg/kg) at Dar es Salaam port.…”