Differences in Trace Element Content between Non-Indigenous Farmed and Invasive Bivalve Mollusks of the South African Coast

Abstract

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.

Elemental composition and bioaccessibility of farmed oysters (Crassostrea gigas) fed different ratios of dietary seaweed and microalgae during broodstock conditioning

“…Regarding the remaining elements, Sr and Br contents were similar to the values reported for C. gigas in the South African Atlantic Coast, 45 ± 5 mg/ kg dw and 127 ± 10 mg/kg dw, respectively. In this study, the I content was lower than that of the South African oysters, 10.9 ± 0.4 mg/ kg dw (Pavlov et al, 2015). This is noteworthy, especially for SW100 oysters, which were fed a SW feed rich in I (44.6 ± 0.8 mg/kg dw).…”

“…This phenomenon does not seem to result from a lower metabolic rate in the SW0 oysters. A low metabolic rate is sometimes an explanation for low accumulation rates (Pavlov et al, ). Indeed, the viability results associated with this study on broodstock conditioning of C. gigas (Rato et al, ) have shown that SW100 oysters exhibited a higher mortality when compared to SW0 and the remaining feeds, being unable to meet the demands for maintenance—a lower standard metabolic rate was measured in the SW100 oysters than in SW0 oysters (Ozório et al, ).…”

“…The accumulation potential of mineral elements by bivalves is well known (Amiard et al, ; García‐Rico & Ruiz, ; Pavlov, Bezuidenhout, Frontasyeva, & Goryainova, ), and, in particular, oyster meat is typically rich in both macro elements and trace metals (Asha, Anandan, Mathew, & Lakshmanan, ). For instance, Indian backwater oyster ( Crassostrea madrasensis ) contained substantial levels of Zn and Se (Chakraborty, Chakkalakal, Joseph, & Joy, ).…”

“…This phenomenon does not seem to result from a lower metabolic rate in the SW0 oysters. A low metabolic rate is sometimes an explanation for low accumulation rates (Pavlov et al, 2015).…”

Trace Elements in Mediterranean Mussels Mytilus galloprovincialis from the South African West Coast

“…According to both the ICP-MS and NAA results, As exhibited the most notable differences. These site-specific differences in the contents of determined elements in the tissues of the mussels can be explained by the differences in the environmental conditions at these sites as suggested by Pavlov et al [13]. The conditions in Danger Bay are more dynamic and challenging for the mussels as they inhabit rocks that are exposed to extreme weather conditions, opposed to the mussels in Saldanha Bay that are always submerged.…”