Retention and distribution of methylmercury administered in the food in marine invertebrates: Effect of dietary selenium

Exposure to methylmercury and inorganic mercury in the food does not lead to trophic magnification in the sea star Asterias rubens

“…The feeding rates for A. rubens on mussels increased with temperature at temperatures between 1⁰C and 12⁰C (Aguera et al, 2012) and St-Pierre and Gagnon (2015) demonstrated approximately identical feeding rates (also on mussels) at 11⁰C and 15⁰C but only 64% and 38% of this feeding rate at than at 5⁰C and 2⁰C, respectively. Although both accumulation and elimination rates might be hypothesized to be higher during summer than shown in the present autumn-winter-spring experiments, the halflife of 181 d for methylmercury determined at 10⁰C (Bjerregaard et al, 2018) was similar to the half-life (173 d) in the slowly exchanging compartment at 4⁰C to 8⁰C in the present experiment.…”

“…Ad 3) Laboratory experiments show that methylmercury may be retained very efficiently in fish -especially in larger fish -with half-lives of more than one year (summarized by Trudel and Rasmussen, 1997) and Madenjian et al (2021) suggest that results obtained in the laboratory actually may underestimate real retention times in the field. Most investigations of retention of methylmercury in decapod crustaceans also show half-lives in the range of 1 to 2 years (Bjerregaard and Christensen, 2012;Bjerregaard et al, 2018;Evans et al, 2000;Fowler et al, 1978;Headon et al, 1996;Larsen and Bjerregaard, 1995;Miettinen et al, 1972;Rouleau et al, 1999;Tillander et al, 1969). Sea stars eliminate methylmercury faster [T½ = 173 to 181 d present study and (Bjerregaard et al, 2018) ] than both fish and decapods.…”

“…Most investigations of retention of methylmercury in decapod crustaceans also show half-lives in the range of 1 to 2 years (Bjerregaard and Christensen, 2012;Bjerregaard et al, 2018;Evans et al, 2000;Fowler et al, 1978;Headon et al, 1996;Larsen and Bjerregaard, 1995;Miettinen et al, 1972;Rouleau et al, 1999;Tillander et al, 1969). Sea stars eliminate methylmercury faster [T½ = 173 to 181 d present study and (Bjerregaard et al, 2018) ] than both fish and decapods. Inorganic mercury is generally retained less efficiently in fish than methylmercury with 3-fold higher excretion rates (Trudel and Rasmussen, 1997) and decapod crustaceans also show lower half-lives for inorganic mercury than for methylmercury [T½ = 112 d in the shrimp Lysmata seticaudata (Fowler et al, 1978) and 56 days in the shore crab C. maenas (Larsen and Bjerregaard, 1995)].…”

“…A. rubens accumulates mercury from both water (Rouleau et al, 1993;Sorensen and Bjerregaard, 1991) and from food in short-term experimental investigations (Bjerregaard et al, 2018) and so does the starfish Leptasterias polaris (Maheu and Pelletier, 1994;Pelletier and Larocque, 1987;Rouleau et al, 1995a, b) in different experimental settings. It is not known if prolonged exposure to methylmercury and inorganic mercury in the food will lead to trophic magnification [here defined as increase in concentration from one step in the food chain to the next] of mercury in A. rubens.…”

Do Two Wrongs Make a Right? Persistent Uncertainties Regarding Environmental Selenium–Mercury Interactions

“…Observations of in vivo sequestration or redistribution of Hg following elevated Se exposures within individuals support this hypothesis. For example, field collections of aquatic organisms report insoluble HgSe precipitate formation in tissues where detoxification processes occur (e.g., liver and kidney), ,,− while experiments co-administering Se and Hg find that certain forms of Se (SeIV, SeMet, and SeCys, but not SeVI) lead to Hg redistribution among tissues and elimination from terrestrial and aquatic organisms. ,− Together, these studies suggest that Hg is either demethylated or becomes biologically unavailable for in vivo methylation when Se is present in molar excess of Hg (i.e., Se:Hg > 1). ,, Se-mediated demethylation, redistribution, and sequestration of Hg could thus theoretically result in decreased bioavailability and bioaccumulation of Hg to higher trophic species. At the ecosystem-scale, there is associative evidence for Se mediation of Hg in food webs.…”