Comparative effects of trace metal elements released from dissolution of aluminum-based galvanic anodes, aluminum chloride, zinc chloride, and their mixture on the development of the Pacific oyster D-larvae, Crassostrea gigas.

As the most abundant metal in the earth's crust, aluminum (Al) is used in many sectors, and nowadays, there is an increase in anthropogenic releases to aquatic ecosystems. This is particularly true in the context of corrosion protection systems involving galvanic anodes, which are mostly made of Al. Corroded instead of the steel structures they protect, galvanic anodes are described as sacrificial anodes. In contact with seawater, they undergo oxidation and release various metals in the form of ions or oxy-hydroxides into the marine environment, mainly Al and zinc (Zn). Several studies agree that Al increases the incidence of abnormal development in bivalve larvae from 150 μg L-1 which is close to the highest Al concentrations recorded in coastal waters. Therefore, we studied the impact of the cocktail of metals released by aluminum-based galvanic anodes on the development of Crassostrea gigas larvae, which we compared to the effects of aluminum chloride hexahydrate and zinc chloride alone and their mixture. The anode solution was realized thanks to an experimental device simulating the dissolution of a galvanic anode in the marine environment in order to reproduce the cocktail of metal species. We calculated an EC50 of 193.55 μg L-1 and 100.05 μg L-1 for Al and Zn chloride alone, respectively, and we highlighted an EC50 of 190.22 μg L-1 for the galvanic anode based on Al concentration. The mixture of the two metals in their chloride form resulted in the observation of additive and synergistic effects, which underlines the importance of considering the cocktail effect in ecotoxicological studies.