Bioaccumulation and public health implications of trace metals in edible tissues of the crustaceans Scylla serrata and Penaeus monodon from the Tanzanian coast

Abstract

The coastal population in East Africa is growing rapidly but sewage treatment and recycling facilities in major cities and towns are poorly developed. Since estuarine mangroves are the main hotspots for pollutants, there is a potential for contaminants to accumulate in edible fauna and threaten public health. This study analysed trace metals in muscle tissues of the giant mud crabs (Scylla serrata) and the giant tiger prawns (Penaeus monodon) from the Tanzanian coast, in order to determine the extent of bioaccumulation and public health risks. A total of 180 samples of muscle tissues of S. serrata and 80 of P. monodon were collected from nine sites along the coast. Both species showed high levels of trace metals in the wet season and significant bioaccumulation of As, Cu and Zn. Due to their burrowing and feeding habits, mud crabs were more contaminated compared to tiger prawns sampled from the same sites. Apart from that, the measured levels of Cd, Cr and Pb did not exceed maximum limits for human consumption. Based on the current trend of fish consumption in Tanzania (7.7 kg/person/year), the measured elements (As, Cd, Co, Cu, Mn, Pb and Zn) are not likely to present health risks to shellfish consumers. Nevertheless, potential risks of As and Cu cannot be ruled out if the average per capita consumption is exceeded. This calls for strengthened waste management systems and pollution control measures.

Accumulation and health risk assessment of heavy metals in tissues of the shrimp and fish species from the Yumurtalik coast of Iskenderun Gulf, Turkey

“…They are pollutants that can stay in water environments for long periods without decomposing and cause damage to water organisms. The increase in heavy metal levels left over to the marine environment in recent years results in extensive research on marine pollution [1, 2]. Heavy metals are among the major environmental pollutants entering the food chain.…”

Genetic diversity and connectivity in the East African giant mud crab Scylla serrata: Implications for fisheries management

“…The growing coastal population is also threatening the sustainability of mud crab fisheries due to increased incidences of pollution [ 13 , 14 ], and mangrove degradation [ 15 ]. In general, 1.25% of the existing African mangrove forest is lost each year [ 16 ].…”

Ecdysis as an auxiliary route for the removal of heavy metals in crustaceans: Laboratory analysis with native mangrove specimens

“…Among these ecosystems, the estuarine environment is one of the most contaminated by metallic compounds, which seriously affect the physiology of the organisms exposed to these contaminants (Capparelli et al 2017;Portner 2010;Veríssimo et al 2013). Organisms, such as crustaceans, exposed for a long time to these metallic contaminants, when they survive, end up accumulating them directly or indirectly through contact with contaminated water, substrate, and food intake (Boyd 2010;Oliveira et al 2013; Rumisha et al 2017). As the bioaccumulation process is continuous, this will provide the absorption of heavy metals by different tissues of native crustaceans, accrediting them to sensitive indicators of environmental degradation (Bergey & Weis 2007;Kannan et al 2016;Capparelli et al 2016Capparelli et al , 2017 However, these species have detoxi cation mechanisms to deal with these contaminants, such as the production of metal granules linked to metallothionein, performed by the hepatopancreas, or the secretion of metal salts by osmosis made by the gills (Capparelli et al 2017;Martins et al 2011;Mazzei et al 2014;Pinheiro et al 2012).…”