Accumulation of total mercury in deep-sea sediments and biota across a bathymetric gradient in the Southeastern Mediterranean Sea

Guy Sisma-Ventura, Jacob Silverman, Tamar Guy-Haim, Nir Stern, Aviv Shachnai, Maya Mar Mori, Maria Abu Khadra, Yitzhak Jacobson, Yael Segal, Timor Katz, Barak Herut

Research output: Contribution to journalArticlepeer-review

Abstract

This study explores the accumulation of total mercury (THg) in deep-sea sediments and demersal megafauna of the ultra-oligotrophic Southeastern Mediterranean Sea (SEMS) across bathymetric gradients in the range 35–1900 m, sampled in seven cruises during 2013, 2017–2021, and 2023. Measurements of THg were conducted in surficial (0.0–0.5 cm) and subsurface (9.0–10 cm) sediments, demersal sharks, demersal teleost fish, and benthic crustaceans. Sedimentary organic carbon and biota δ13C and δ15N values were determined to explore possible foraging habitats and dietary sources of THg. The results exhibit an increasing trend of THg in surficial sediments with increasing bottom depth, while in the subsurface, pre-industrial sediments, THg remains lower, slightly increasing with depth. Having no major terrestrial point sources in this area, this increasing trend of THg in surficial sediments across bathymetric gradients is controlled by atmospheric mercury deposition, scavenged by the biological pump, and by lateral transport of particulate Hg in winnowed fine particles from the shelf. Similarly, the THg in benthic crustaceans and demersal fish ranged between 0.02 and 2.71 μg g−1 wet weight (0.06 and 10.8 μg g−1 dry weight) and increased with muscle δ13C as a function of distance offshore, while presenting a low THg-δ15N bio-magnification power. Our results suggest that foraging habitats, longevity, and species-specific depth distribution control their muscle THg bioaccumulation. Despite this complexity, the pooling of THg in megafauna into specific deep zones reflected the trend of increasing anthropogenic THg across bathymetric gradients. Furthermore, many of the biota measurements exceeded safe consumption thresholds for Hg and therefore, should be considered carefully in the development and regulation of deep-sea trawling in this region.

Original languageAmerican English
Article number141201
JournalChemosphere
Volume351
DOIs
StatePublished - Mar 2024

Keywords

  • Bathymetric gradient
  • Deep-sea habitats
  • Mercury bioaccumulation
  • Southeast Mediterranean Sea
  • Stable isotopes

All Science Journal Classification (ASJC) codes

  • General Chemistry
  • Public Health, Environmental and Occupational Health
  • Pollution
  • Health, Toxicology and Mutagenesis
  • Environmental Engineering
  • Environmental Chemistry

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