Balzani et al. 2026 — Metal accumulation and biomagnification in three commercially important fish from Dalyan Lake, Türkiye
Balzani and colleagues measured chromium (Cr), nickel (Ni), arsenic (As), and lead (Pb) in the dorsal muscle of 27 commercially important fish from Dalyan Lake, a brackish coastal lagoon in the Turkish Aegean, and combined contaminant data with carbon and nitrogen stable isotope analysis to assess trophic transfer. Concentrations were low across all four metals and all three species, with As showing the clearest interspecific pattern (highest in the more sediment-associated gilthead seabream), while Cr was the only metal showing evidence of biomagnification; As, Ni, and Pb showed trophic dilution rather than biomagnification. The context is a brackish lagoon near the Aegean coast, not an open-sea commercial fishery, so values reflect a specific enclosed-water environment that may not be representative of market fish from the broader Mediterranean or global seafood supply chains.
Key numbers
All concentrations in µg/kg dry weight (ICP-MS, n=9 per species):
Arsenic (tAs):
- Sparus aurata (gilthead seabream): 2.07 µg/kg
- Mugil cephalus (grey mullet): 1.49 µg/kg
- Dicentrarchus labrax (European seabass): 1.06 µg/kg
Chromium (Cr):
- Mugil cephalus: 1.58 µg/kg
- Sparus aurata: 1.47 µg/kg
- Range across species: 1.47–1.58 µg/kg; Cr showed biomagnification
Nickel (Ni):
- All species: 0.51–0.56 µg/kg (D. labrax highest at 0.56)
Lead (Pb):
- Mugil cephalus: 0.47 µg/kg
- Dicentrarchus labrax: 0.25 µg/kg
- Range: 0.25–0.47 µg/kg
LOD: Cr=0.0000621 µg/mL, Ni=0.0000083 µg/mL, As=0.0000058 µg/mL, Pb=0.0000038 µg/mL. RSD 1–5% for all metals. Values below LOD substituted with LOD value itself.
Methods (brief)
Muscle samples (dorsal) from 27 fish (9 per species) caught by multi-mesh gillnets at Dalyan Lake, summer 2021. Digested and measured by ICP-MS (Eskişehir Osmangazi University Center Research Laboratory). Concentrations reported in µg/kg dry weight after conversion. Stable isotope analysis (δ13C, δ15N) by isotope ratio MS (Delta V Advantage, Thermo Fisher Scientific) at Akdeniz University. As speciation not performed; values are total arsenic only. No Hg, Cd, or Al measurements in this study.
Implications
Certification: Concentrations in all metals are exceptionally low even for a lagoon environment, consistent with Dalyan Lake being a comparatively clean aquatic system. These values fall far below EU Maximum Residue Levels for fish (e.g., EU Pb limit for fish muscle 0.3 mg/kg = 300 µg/kg; these samples are at 0.25–0.47 µg/kg). Not directly applicable to broad seafood safety benchmarks but documents the trophic-dilution behavior of As, Ni, Pb in food-web contexts.
Courses: Good case study for explaining why biomagnification is metal-specific; Cr biomagnifies but As undergoes trophic dilution in this food web, contrasting with mercury’s well-known biomagnification pattern.
App: Values here are extremely low and represent a low-contamination brackish lagoon scenario; not appropriate to use as typical seafood contamination estimates for general seafood categories.