Impact of a Sacrificial Anode as Assessed by Zinc Accumulation in Different Organs of the Oyster Crassostrea gigas: Results from Long- and Short-Term Laboratory Tests

Abstract

Sacrificial anodes made of zinc are currently used in marine environments to mitigate marine corrosion as part of CP systems of immerged metallic structures. The aim of this work was to study zinc bioconcentration in the oyster Crassostrea gigas by performing two in vivo tests during different time periods and at different zinc concentrations. The first test was conducted during a period of 10weeks at a concentration of 0.53±0.04mg Zn L(-1) to simulate long-term exposure, and a second test was conducted during a 168-hour period at a concentration of 10.2±1.2mg Zn L(-1) to reproduce short-term exposure. In these experiments, the zinc source was an electrochemical device that included a sacrificial anode to mimic the in situ conditions. During the first 14days of the long-term experiment, digestive glands of C oysters exhibited bioaccumulation of zinc that varied according to the oysters' reproductive cycle. Both a bioconcentration factor (BCF) of≤13,397 and a zinc accumulation percentage of +297% of zinc occurred in this organ after 10weeks. The results obtained from the short-term test showed a lower BCF of 405 but a faster bioaccumulation of zinc (starting from the first day) in the same organ. No mortality was observed in long-term assay, but 81.8% of the oysters died at the end of the short-term assay. These results demonstrate the great capacity of C. gigas to accumulate zinc released from the anode, especially when low concentrations are released, as in the case of anode dissolution used as CP. This study confirmed the necessity to monitor this zinc-contamination source in marine environments in relation to the usual oyster consumption by humans (especially in France). No implication for human health of this zinc-contamination source was demonstrated until now, and this was not the purpose of this study; however, zinc remains one of the most abundant nutritionally essential elements in the human body that may affect the human immune system at high-level uptake.