Environmental behaviors and toxicity of heavy metals and metallic nanoparticles to marine organisms under ocean acidification

Since industrial revolution, anthropogenic carbon dioxides releasing into the atmosphere are absorbed by the global oceans, which leads to measurable decrease of surface seawater pH and carbonate ion concentration ([CO 3 2− ]), thus causing the acidification of global ocean. Besides direct threatening the stability of marine ecosystems, ocean acidification (OA) could also change the environmental processes of marine pollutants, thus indirectly influencing their toxicity to marine organisms. By selecting heavy metals and metallic nanoparticles (MNPs) as the model marine pollutants, this review deeply summarizes the dominant mechanisms on species changes of heavy metals, and the dissolution, dispersion and transport of MNPs based on the causes of OA. The effects of OA-induced environmental process alteration on the toxicity of heavy metal and MNPs to marine organisms at different levels are explored. The differences among the observed toxicological data are analyzed. Finally, the key research challenges and future directions on the toxicity of OA and coexisting pollutants are provided.