Toxic Effect of Metal-Based Nanomaterials on Representatives of Marine Ecosystems: A Review

The review summarizes the recent data on the toxic effect that engineered metal nanoparticles (NPs) and their oxides (Ag, Au, Cu, CuO, zero-valent iron, TiO2, and ZnO) exert on marine organisms of various taxonomic groups. Toxicity is considered with due regard of the size effects and physicochemical properties of NPs. Available data indicate that metallic NPs may adversely affect algae, bacteria, mollusks, worms, arthropods, echinoderms, chordates, etc. Toxic effects vary from reproductive disorders to death. Only scarce data are available on the NP effect on marine vertebrates (e.g., marine fish). The factors that affect the NP toxicity in an aqueous environment include the physicochemical properties of NPs, species specificities of the test organism, and parameters of the aqueous environment (in particular, salinity, temperature and pH). Exact relationships between the factors and NP toxicity are still poorly understood. In particular, there is no consensus on how salinity affects the NP toxicity in an aqueous environment. Putative mechanisms of NP toxicity include oxidative stress, impaired cell membrane integrity, inflammatory processes with consequent cell dysfunction, DNA damage, and genetic mutations. NPs easily persist within organisms and consequently have a high potential to accumulate in marine food chains. Lack of standardized techniques to detect metallic and metal oxide NPs and weak or absent relevant legislation complicate toxicology studies in marine ecosystems. The above circumstances make it necessary to further evaluate the safety of metallic NPs for marine organisms and especially vertebrates, to study the distant effects associated with NP transition and accumulation in marine food chains, and to unify the respective research protocols. The exact role of environmental factors in modulating NP toxicity and the mechanisms of NP toxicity are also important issues to address in future studies.