Species-specific mercury speciation in billfishes and its implications for food safety monitoring and dietary advice.

Humans are exposed to toxic methylmercury mainly by consuming marine fish, in particular top predator species like billfishes or tunas. In seafood risk assessments, mercury is assumed to be mostly present as organic methylmercury in predatory fishes; yet high percentages of inorganic mercury were recently reported in marlins, suggesting markedly different methylmercury metabolism across species. We quantified total mercury and methylmercury concentrations in muscle of four billfish species from the Indian and the Pacific oceans to address this knowledge gap.

Trace element uptake by macroalgae: Organic colloids as a source of metals, including Fe and rare earth elements.

We determined the concentrations of trace elements including Fe, Al, rare earth elements and Y (REY), in Ascophyllum nodosum, one of the most abundant brown macroalgae in the North Atlantic. Samples were collected in the Bay of Brest (Brittany, France) and in the estuary of its main contributing river. The Y/Ho, Al/Ga, and Zr/Hf ratios display values distinctive from seawater, but similar to the continental crust; an observation which we show cannot be explained by the incorporation of terrigenous particles, nor inorganic colloids.