Stable isotope ratios of carbon, nitrogen and sulphur and mercury concentrations as descriptors of trophic ecology and contamination sources of Mediterranean whales

Marianna Pinzone; France Damseaux; Loïc N Michel; Krishna Das

doi:10.1016/j.chemosphere.2019.124448

Stable isotope ratios of carbon, nitrogen and sulphur and mercury concentrations as descriptors of trophic ecology and contamination sources of Mediterranean whales

Chemosphere. 2019 Dec:237:124448. doi: 10.1016/j.chemosphere.2019.124448. Epub 2019 Jul 24.

Authors

Marianna Pinzone¹, France Damseaux², Loïc N Michel³, Krishna Das⁴

Affiliations

¹ Freshwater and Oceanic Sciences Unit of ReSearch (FOCUS), Laboratory of Oceanology, University of Liège B6c, 11 Allée du 6 Août, 4000 Liège, Belgium. Electronic address: mpinzone@uliege.be.
² Freshwater and Oceanic Sciences Unit of ReSearch (FOCUS), Laboratory of Oceanology, University of Liège B6c, 11 Allée du 6 Août, 4000 Liège, Belgium. Electronic address: fdamseaux@uliege.be.
³ Freshwater and Oceanic Sciences Unit of ReSearch (FOCUS), Laboratory of Oceanology, University of Liège B6c, 11 Allée du 6 Août, 4000 Liège, Belgium.
⁴ Freshwater and Oceanic Sciences Unit of ReSearch (FOCUS), Laboratory of Oceanology, University of Liège B6c, 11 Allée du 6 Août, 4000 Liège, Belgium. Electronic address: krishna.das@uliege.be.

PMID: 31398606
DOI: 10.1016/j.chemosphere.2019.124448

Abstract

The Mediterranean Sea remains a complex system for mercury (Hg) cycling and accumulation in marine vertebrates. The extremely high levels these animals present demand for an urgent understanding of such processes and the development of new analytical techniques that go beyond the simple contamination monitoring. It was often proposed that prey selection or habitat use may affect Hg contamination in animals; however, it was never possible to measure which factor influences more rates and pathways of contamination. In this paper, we directly integrate toxicological information (Hg levels) and ecological tracers (stable isotopes of C, N and S) into a common data analysis framework (isotopic niches), with the aim of quantifying the influence of species' trophic behaviour on Hg contamination. The analysis was conducted on skin biopsies of fin whales Balaenoptera physalus, long-finned pilot whales Globicephala melas and sperm whales Physeter microcephalus. Their different trophic modes and residency in the area make them model species for the analysis of Hg accumulation along NWMS food webs. We measured Total Hg (T-Hg) concentrations through absorbance spectrometry with the DMA80 Milestone. Carbon, nitrogen and sulphur isotope compositions were measured via mass spectrometry in an IRMS coupled to an Elemental Analyser (EA) Isoprime. Comparison of ecological and contamination niches allowed to explain Hg accumulation in Mediterranean marine predators. Factors such as food web complexity, trophic position, hunting distribution or habitat use (e.g., foraging depth) did not influence Hg exposure. It is rather the selection of prey type, which determines the range of potential Hg sources and as a consequence the rates of accumulation in whales' tissues. A generalist piscivorous species such as the pilot whales will bioaccumulate more Hg than specialised sperm whales feeding mostly on cephalopods.

Keywords: Cetaceans; Contamination niche; Diet specialisation; Ecological niche; Mediterranean sea; Mercury.

MeSH terms

Animals
Carbon Isotopes / analysis
Ecology*
Environmental Monitoring*
Fin Whale / metabolism
Food Chain*
Isotopes / analysis*
Mediterranean Sea
Mercury Isotopes / analysis
Nitrogen Isotopes / analysis
Sperm Whale / metabolism
Sulfur Isotopes / analysis
Water Pollutants, Chemical / analysis
Whales / metabolism*
Whales, Pilot / metabolism

Substances

Carbon Isotopes
Isotopes
Mercury Isotopes
Nitrogen Isotopes
Sulfur Isotopes
Water Pollutants, Chemical