Effects of chronic exposure of metals released from the dissolution of an aluminium galvanic anode on the Pacific oyster Crassostrea gigas.

Among the anthropogenic sources releasing metallic species into the marine environment, the galvanic anode cathodic protection system (GACP) is widely used to protect submerged metallic structures from corrosion. Galvanic anodes are an alloy of metals of which the main component is aluminum or zinc. Very few studies were performed to study their potential biological effects. We investigated the chronic toxicity of an aluminum-based galvanic anode on the Pacific oyster, Crassostrea gigas. Oysters were exposed for 84 days to three concentrations of aluminum (50, 100 and 300 µg L) obtained with an electrochemical experimental device simulating the dissolution of a galvanic anode. At different exposure times, we studied a battery of biomarkers of the immune system, reproductive parameters and the metabolic state of the oysters. Results demonstrated a sensitivity of oysters at the highest concentration and some biological effects were observed especially for the malondialdehyde content in the digestive gland after 84 days of exposure. In addition to these biomarkers, the bioaccumulation of the different metals composing the anode was measured in oysters' tissues. Bivalves bioaccumulated more zinc than aluminum, even if aluminium was present in greater concentrations during exposures. Moreover, exposure time did not influence the bioaccumulation of aluminum in contrast to zinc.