Rare earth elements as emerging contaminants in marine ecosystems: Bioaccumulation and ecological implications

Rare earth elements (REEs) are increasingly recognized as environmental contaminants due to their widespread industrial use and release into marine ecosystems. This review synthesizes current knowledge on REE bioaccumulation across marine taxa, highlighting interspecies differences and regional variability. Primary producers such as macroalgae exhibit the highest ∑REE levels (up to 2,975,705 μg kg^-1, with yttrium 2,647,050 μg kg^-1 and europium 23,872 μg kg^-1), while bivalves also accumulate substantially (mean ∑REE ≈ 391,283 μg kg^-1; maxima exceeding 4.3 million μg kg^-1 in Mytilus galloprovincialis). In contrast, secondary consumers show reduced concentrations, with fish (6018 μg kg^-1), crabs (13,271 μg kg^-1), shrimp (1951 μg kg^-1), birds (940 μg kg^-1), and mammals (4428 μg kg^-1), reflecting limited biomagnification. Regionally, Japan (11.4 million μg kg^-1) and the Black Sea (9.8 million μg kg^-1) exhibit extreme REE enrichment, whereas the North Atlantic (29 μg kg^-1) shows minimal accumulation. Toxicological evidence indicates oxidative stress and reproductive impairments in marine species, raising concerns for ecosystem health and seafood safety. Addressing current knowledge gaps through standardized monitoring is critical for assessing REE pollution's ecological and human health risks.