What question did this study set out to answer?

The study aims to investigate the concentrations and distribution patterns of rare earth elements in the muscle tissue of common Black Sea fish.

April 13, 2026Open Access

Rare earth elements in muscle tissue of common Black Sea fish: Concentrations, fractionation patterns, biochemical associations, and human health risk assessment

Key Points

The study aims to investigate the concentrations and distribution patterns of rare earth elements in the muscle tissue of common Black Sea fish.
Analyzed muscle tissue from eight fish species in the northern Black Sea.
Measured total rare earth element concentrations and their fractionation patterns.
Evaluated correlations between rare earth elements and biochemical components like protein and minerals.
Total REE concentrations ranged from 0.25 mg·kg−1 to 1.33 mg·kg−1.
Demersal and benthopelagic species showed higher REE levels compared to pelagic species.
Identified anomalies for La, Eu, Tb, Tm, and Lu in enrichment factor patterns.
Found significant positive correlations between ΣREEs and protein, Ca, and Zn.

Abstract

Rare earth elements (REEs) are emerging contaminants in marine environments, but their occurrence and behavior in edible fish tissues are still poorly characterized. This study examined concentrations, distribution patterns, and fractionation of REEs in the muscle tissue of eight common fish species from the northern Black Sea, representing pelagic, demersal, and benthopelagic habitats. Total REE concentrations (ΣREE) ranged from 0.25 mg·kg −1 (in Sprattus sprattus and Alosa immaculata ) to 1.33 mg·kg −1 dry weight (in Mullus barbatus ), exceeding median values reported for marine fish from other regions. Demersal and benthopelagic species generally exhibited higher ΣREE levels. Normalized REE patterns revealed clear species-specific fractionation. Enrichment factors indicated anomalies for La, Eu, Tb, Tm, and Lu, reflecting combined natural and anthropogenic contributions. Light REE enrichment, expressed by elevated (La/Yb) N ratios, occurred in Alosa immaculata , Engraulis encrasicolus , Scorpaena porcus , and Trachurus mediterraneus , whereas light REE depletion characterized Mullus barbatus and Spicara flexuosum . Intermediate Ho Y correlation slopes highlighted the influence of terrestrial inputs. Significant correlations between ΣREEs, Ca, Zn, and total protein content suggest that REEs in fish muscle are primarily associated with protein-rich and phosphate-containing biochemical fractions. No likely human health risks associated with REEs were identified from the daily consumption of muscle tissue of the studied fish species at ingestion rates typical for the local population. These findings advance understanding of REE behavior in marine fish and support continued monitoring of REEs in coastal ecosystems. • REE accumulation in fish muscle is species- and habitat-specific. • Demersal and benthopelagic species are generally richer in ΣREE. • Anomalies for La, Eu, Tb, Tm, and Lu are identified in enrichment factor patterns. • REEs positively correlate with protein, Na, Mg, P, Ca, and Zn in fish muscle. • Protein-bound REE accumulation occurs in edible tissues.

Rare earth elements in muscle tissue of common Black Sea fish: Concentrations, fractionation patterns, biochemical associations, and human health risk assessment

Key Points

Abstract

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