The contents of 23 trace elements (Sc, V, Cr, Mn, Fe, Co, Zn, As, Se, Br, Rb, Sr, Mo, Ag, Sb, I, Ba, La, Ce, Sm, Eu, Hf, Ta) were quantitatively determined in soft tissues and shells of mass non-indigenous bivalve mussels-farmed Pacific oysters (Crassostrea gigas) and farmed and wild invasive Mediterranean mussels (Mytilus galloprovincialis) at the Atlantic coast of South Africa. The study revealed that the contents of the majority of elements in the soft tissues of both species were higher than those in the shells. The tissues of wild invasive Mediterranean mussels contain higher levels of a range of trace elements comparing to farmed mussels. The tissues of Pacific oysters contain much higher levels of almost all elements studied compared to the tissues of Mediterranean mussels. Higher content of zinc in the mussels and oysters from Saldanha Bay may evidence anthropogenic pollution of the bay's ecosystem by this metal, which necessitates continued monitoring of levels of potentially toxic metals. Both alien species, and especially Pacific oysters, may serve as reliable biomonitors for trace elements in marine ecosystems. Both species are rich in essential elements and provide nutritionally-valuable seafoods.

TRACE ELEMENTS IN MEDITERRANEAN MUSSELS Mytilus galloprovincialis FROM THE SOUTH AFRICAN WEST COASTPIERWIASTKI ŚLADOWE W ŚRÓDZIEMNOMORSKICH MAŁŻACH Mytilus galloprovincialis Z POŁUDNIOWEGO WYBRZEŻA AFRYKI ZACHODNIEJ Abstract: Invasive bivalve molluscs, Mediterranean mussels (Mytilus galloprovincialis) were used as sentinel biomonitors of pollution by inorganic contaminants in Saldanha Bay and the Langebaan Lagoon area of South Africa. Two complementary analytical techniques, ICP-MS and NAA, allowed for determination of concentrations of 31 major and trace elements including heavy metals and arsenic in the soft tissues of the mussels. Distinct seasonal patterns were found in the dynamics of these concentrations, with the mussels accumulating much more trace elements in winter than in the summer. In general, the mussels that grew naturally also demonstrated higher concentrations of As, Cd, Fe, Hg and Zn than those that were farmed. Fe showed the highest levels with a maximum concentration of 444 mg/kg followed by Zn with a maximum of 228 mg/kg. The concentrations of Mn and Pb were significantly higher in the Port of Saldanha close to the jetty where ores containing these metals are loaded in comparison with the other sampling sites. It was concluded that bivalve molluscs present themselves as effective biomonitors when assessing marine aquatic pollution by inorganic contaminants in the Saldanha Bay region.

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