Evaluating mercury biomagnification in fish from a tropical marine environment using stable isotopes (δ13C and δ15N)

Hassan A. Al-Reasi, Fuad A. Ababneh, David R. Lean

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Abstract

Concentrations of total mercury (T-Hg) and methylmercury (MeHg) were measured in zooplankton and 13 fish species from a coastal food web of the Gulf of Oman, an arm of the Arabian Sea between Oman and Iran. Stable isotope ratios (δ13C and δ15N) also were determined to track mercury biomagnification. The average concentration of T-Hg in zooplankton was 21 ± 8.0 ng g-1 with MeHg accounting 10% of T-Hg. Total mercury levels in fish species ranged from 3.0 ng g-1 (Sardinella longiceps) to 760 ng g-1 (Rhizoprionodon acutus) with relatively lower fraction of MeHg (72%) than that found in other studies. The average trophic difference (Δδ13C) between zooplankton and planktivorous fish (Selar crumenopthalmus, Rastrelliger kanagurta, and S. longiceps) was higher (3.4‰) than expected, suggesting that zooplankton may not be the main diet or direct carbon source for these fish species. However, further sampling would be required to compensate for temporal changes in zooplankton and the influence of their lipid content. Trophic position inferred by δ15N and and slopes of the regression equations (log10[T-Hg] = 0.13[δ15N] - 3.57 and log 10[MeHg] = 0.14[δ15N] - 3.90) as estimates of biomagnification indicate that biomagnification of T-Hg and MeHg was lower in this tropical ocean compared to what has been observed in arctic and temperate ecosystems and tropical African lakes. The calculated daily intake of methylmercury in the diet of local people through fish consumption was well below the established World Health Organization (WHO) tolerable daily intake threshold for most of the fish species except Euthynnus affinis, Epinephelus epistictus, R. acutus, and Thunnus tonggol, illustrating safe consumption of the commonly consumed fish species.

Original languageEnglish
Pages (from-to)1572-1581
Number of pages10
JournalEnvironmental Toxicology and Chemistry
Volume26
Issue number8
DOIs
Publication statusPublished - Aug 2007

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Keywords

  • Fish
  • Gulf of Oman
  • Methylmercury
  • Total mercury
  • Trophic positions

ASJC Scopus subject areas

  • Environmental Science(all)
  • Environmental Chemistry
  • Toxicology
  • Health, Toxicology and Mutagenesis

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