[MARMAM] new publication - Hg and Se in Caribbean cetaceans taken for human consumption

Russell Fielding rtfieldi at sewanee.edu
Fri Nov 22 06:18:45 PST 2019


Dear MARMAM list members,



On behalf of my coauthors, I am pleased to share our recent study on
mercury and selenium concentrations, and selenium:mercury molar ratios, in
several species of small cetaceans taken for human consumption in St.
Vincent & the Grenadines. The paper is currently in press with *Environmental
Research* and can be accessed here:



https://www.sciencedirect.com/science/article/pii/S0013935119307054



Abstract:

This study measured the concentration of total mercury (THg) and selenium
(Se), and calculated the Se:Hg molar ratios in the muscle, blubber, liver,
and kidney of small cetaceans (false killer whale, Pseudorca crassidens;
killer whale, Orcinus orca; Risso's dolphin, Grampus griseus; short-finned
pilot whale, Globicephala macrorhynchus; and dolphins of the genus
Stenella) taken for human consumption off St. Vincent, West Indies.
Overall, 122 samples were analyzed; mean THg concentrations (μg/g dry
weight) were highest in the liver (730), followed by the kidney (274),
muscle (76.4), and blubber (4.57). To explain variability in muscle THg
concentrations, carbon (δ13C) and nitrogen (δ15N) stable isotope ratios
were analyzed to explore differences in dietary carbon source and relative
trophic position, respectively, among species. There was no relationship
between δ15N and THg concentration, but there was a positive relationship
between δ13C and THg concentration. On average for each species, the Se:Hg
molar ratios were>1 in blubber and<1 in muscle. All liver samples and the
majority of kidney, muscle, and blubber samples exceeded the FAO/WHO human
consumption advisory level of 1 μg/g wet weight. Based on our estimations,
consuming only 6.6 g of muscle a week would exceed the MeHg provisional
tolerable weekly intake of 1.6 μg MeHg/kg body weight/week for a 60 kg
person. Given the high THg concentration in these cetaceans and the
frequency at which these tissues are consumed, this is a potential human
health issue that warrants further investigation.


Our key findings include the following:

- Mean wet-weight concentrations of total mercury in muscle, liver, and
kidney from all species sampled, and blubber in the majority of species,
exceed the FAO/WHO advisory level of 1 μg/g

- Our study measured the highest total mercury concentrations reported for
killer whales, which are among the species taken for food in the study area

- Selenium:mercury molar ratios show selenium may have a protective effect
against mercury toxicity in the blubber, is variable in the liver and
kidney, and is unlikely to have a protective effect in muscle

- A potential risk to public health exists in St. Vincent & the Grenadines,
owing to the concentration of mercury found in this popular food product



We hope this paper is of interest to many within the MARMAM community.

Russell Fielding

---
Russell Fielding, Ph.D.
Department of Earth and Environmental Systems
The University of the South
Sewanee, TN 37383 USA
email: russell.fielding at sewanee.edu
web: sewanee.edu/faculty/fielding

*on research leave at the University of the West Indies-Cave Hill
<https://www.cavehill.uwi.edu/>, Barbados (2019-2020)*
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