Abstract
The Lake Zowla-Aného lagoon hydro system, located on the southeast coast of Togo, is very exposed to metal contamination as it receives a huge amount of untreated domestic and industrial effluents from Aného City and the phosphorite treatment plant at Kpémé. This study aims to assess the concentrations of seven heavy metals and their bioaccumulation status in soft tissues and shells of the mangrove oyster (Crassostrea gasar) collected from this aquatic environment. Samples were collected in January, April and July 2017 at two stations and analyzed using flame atomic absorption spectrophotometry. Results indicate that the waters are contaminated by Cd, Pb and Cr with average concentrations that are significantly above WHO standards. At both locations, the contents of the trace elements (except Cr) in oysters’ soft tissues were significantly higher than those in the shells. In the soft tissues, the concentration of Cr, Cu, Zn, As, Cd, Hg, and Pb ranged (in mg·kg-1) from 4.33 to 23.14, 93.4 to 366.7, 455.68 to 1384.15, 0.11 to 1.34, 16.42 to 62.6, 0.05 to 0.473 and 0.39 to 21.08, respectively. Furthermore, statistical analyses showed marked differences in mean concentrations between sampling time on the one hand, and between sampling locations on the other hand (p C. gasar can be used as a biomonitor of Zn, Cd, Cu and Hg exposure. Finally, the Cd, Pb, As, Zn and Cu concentrations in soft tissues and were found to be significantly higher than the permissible limit for human consumption according to WHO and FAO and thus pose a threat to human health.
Highlights
Bivalve molluscs are key components of marine and estuarine environment because, as filter feeders, they play a critical role in maintaining water quality and ecosystem integrity
This study aims to assess the concentrations of seven heavy metals and their bioaccumulation status in soft tissues and shells of the mangrove oyster (Crassostrea gasar) collected from this aquatic environment
We evaluated the Cu, Zn, Cd, Cr, Pb, Hg and As contents in the soft tissue and shell of the mangrove oyster Crassostrea gasar (Dautzenberg, 1891) which, in view of its commercial value and of the volumes landed, is the most important bivalve molluscs caught by the traditional fishery in the Zowla-Aného lagoon system
Summary
Bivalve molluscs are key components of marine and estuarine environment because, as filter feeders, they play a critical role in maintaining water quality and ecosystem integrity. They have been rightfully regarded as “natural functional foods” and their consumption has been common since ancient times [1] [2]. In spite of the fact that some of them are essential at low concentrations for living organisms, at higher concentrations, they could induce toxic effects disturbing organisms’ growth, metabolism, or reproduction with consequences for the entire trophic chain, including humans [7] [8] [9] [10]
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