Differences in metal sequestration between zebra mussels from clean and polluted field locations

Abstract

a b s t r a c tOrganisms are able to detoxify accumulated metals by, e.g. binding them to metallothionein (MT) and/or sequestering them in metal-rich granules (MRG). The different factors involved in determining the capacity or efficiency with which metals are detoxified are not yet known.In this work we studied how the sub-cellular distribution pattern of cadmium, copper and zinc in whole tissue of zebra mussels from clean and polluted surface waters is influenced by the total accumulated metal concentration and by its physiological condition. Additionally we measured the metallothionein concentration in the mussel tissue. Metal concentration increased gradually in the metal-sensitive and detoxified sub-cellular fractions with increasing whole tissue concentrations. However, metal concentrations in the sensitive fractions did not increase to the same extent as metal concentrations in whole tissues. In more polluted mussels the contribution of MRG and MT became more important. Nevertheless, metal detoxification was not sufficient to prevent metal binding to heat-sensitive low molecular weight proteins (HDP fraction). Finally we found an indication that metal detoxification was influenced by the condition of the zebra mussels. MT content could be explained for up to 83% by variations in Zn concentration and physiological condition of the mussels.

Subcellular partitioning profiles and metallothionein levels in indigenous clams Moerella iridescens from a metal-impacted coastal bay

“…S5), suggesting that the "spillover" model is not adequate to represent Cd-handling for M. iridescens when chronically exposed in the field and that Cd detoxification is incomplete as indicated by the presence of Cd in these "inappropriate" fractions. Other researchers have observed similar intracellular partitioning patterns of Cd for relevant organisms (Giguère et al, 2006;Voets et al, 2009;Goto and Wallace, 2010;Rosabal et al, 2015). Notably, the increase in Cd concentrations in HDP fractions seemed to occur early in the bioaccumulation gradients up to a total tissue concentration of approximate 4.5 nmol Cd g −1 dw, and then not show any further increase (Fig.…”

“…3C). We speculate that high Zn concentrations in HSP fraction may respond to the induction of MT-like proteins by essential metals, although [Zn] HSP is also affected by intracellular competition for the MT binding sites because Cu and Cd are known to bind much more strongly to MTs than does Zn (Voets et al, 2009). The only MSF fraction that did show a slightly progressive increase along the Zn bioaccumulation gradient was [Zn] HDP (Fig.…”

“…2) and they are lower for the essential metals, Cu and Zn, than for the non-essential Cd and Pb. This can be explained by the fact that, like most aquatic organisms, M. iridescens can efficiently, at least to a certain extent, regulate uptake and/or excretion of essential metals through homeostatic mechanisms over a wide range of ambient exposure levels, while for the non-essential metals, there appeared to be no, or only a weak, mechanism to regulate or limit uptake or excretion (Voets et al, 2009) tial trace metals with some form of homeostatic control. In this respect, our results are completely in accordance with the findings of other researchers (Bervoets et al, 2004;Bonneris et al, 2005), who also reported that bioaccumulated Cd concentrations were more responsive to the spatial gradients than were those of bioaccumulated Zn, even though the ambient [M] max /[M] min ratios in exposure conditions were less for Cd than for Zn.…”

“…The employment of sentinel organisms as biomonitors of metal contamination is becoming common practice throughout the world (Cooper et al, 2013;Shi and Wang, 2004), where accumulated metals in sentinels can provide valuable information reflecting bioavailability of metal contaminants in the receiving organism's natural habitats (Voets et al, 2009;Wang et al, 2011). Nevertheless, high metal concentrations in organisms or tissues do not give a reliable indication of toxicity, which arises predominantly from the binding of metals to essential biomolecules as a function of internal metabolic availability and the involvement of certain metals in the formation of radicals (Mason and Jenkins, 1995).…”

Corais como organismos biomonitores: aplicação, pré-tratamento e determinação de elementos majoritários e minoritários

“…bivalves e poliquetas, estão o forno de micro-ondas, 44,65,[68][69][70][71][72][73][74][75][76][77][78][79][80] o bloco de aquecimento ou digestor 19,31,55,81-84 e a chapa quente (Tabela 3). 85,86 O uso do forno de micro-ondas foi o procedimento para a digestão de amostras biológicas que se tornou mais popular nas últimas décadas.…”