posted on 2024-02-21, 13:08authored byAnaïs Médieu, David Point, Jeroen E. Sonke, Hélène Angot, Valérie Allain, Nathalie Bodin, Douglas H. Adams, Anders Bignert, David G. Streets, Pearse B. Buchanan, Lars-Eric Heimbürger-Boavida, Heidi Pethybridge, David P. Gillikin, Frédéric Ménard, C. Anela Choy, Takaaki Itai, Paco Bustamante, Zahirah Dhurmeea, Bridget E. Ferriss, Bernard Bourlès, Jérémie Habasque, Anouk Verheyden, Jean-Marie Munaron, Laure Laffont, Olivier Gauthier, Anne Lorrain
Humans are exposed to toxic methylmercury
mainly by consuming
marine
fish. While reducing mercury emissions and releases aims to protect
human health, it is unclear how this affects methylmercury concentrations
in seawater and marine biota. We compiled existing and newly acquired
mercury concentrations in tropical tunas from the global ocean to
explore multidecadal mercury variability between 1971 and 2022. We
show the strong inter-annual variability of tuna mercury concentrations
at the global scale, after correcting for bioaccumulation effects.
We found increasing mercury concentrations in skipjack in the late
1990s in the northwestern Pacific, likely resulting from concomitant
increasing Asian mercury emissions. Elsewhere, stable long-term trends
of tuna mercury concentrations contrast with an overall decline in
global anthropogenic mercury emissions and deposition since the 1970s.
Modeling suggests that this limited response observed in tunas likely
reflects the inertia of surface ocean mercury with respect to declining
emissions, as it is supplied by legacy mercury that accumulated in
the subsurface ocean over centuries. To achieve measurable declines
in mercury concentrations in highly consumed pelagic fish in the near
future, aggressive emission reductions and long-term and continuous
mercury monitoring in marine biota are needed.