Tag Archive for: ecotoxicologie

Evidence that Pacific tuna mercury levels are driven by marine methylmercury production and anthropogenic inputs


Pacific Ocean tuna is among the most-consumed seafood products but contains relatively high levels of the neurotoxin methylmercury. Limited observations suggest tuna mercury levels vary in space and time, yet the drivers are not well understood. Here, we map mercury concentrations in skipjack tuna across the Pacific Ocean and build generalized additive models to quantify the anthropogenic, ecological, and biogeochemical drivers. Skipjack mercury levels display a fivefold spatial gradient, with maximum concentrations in the northwest near Asia, intermediate values in the east, and the lowest levels in the west, southwest, and central Pacific. Large spatial differences can be explained by the depth of the seawater methylmercury peak near low-oxygen zones, leading to enhanced tuna mercury concentrations in regions where oxygen depletion is shallow. Despite this natural biogeochemical control, the mercury hotspot in tuna caught near Asia is explained by elevated atmospheric mercury concentrations and/or mercury river inputs to the coastal shelf. While we cannot ignore the legacy mercury contribution from other regions to the Pacific Ocean (e.g., North America and Europe), our results suggest that recent anthropogenic mercury release, which is currently largest in Asia, contributes directly to present-day human mercury exposure.


Graphical abstract

Spatial variability of skipjack mercury concentrations. Smoothed spatial contour maps of (A) observed and (B) standardized Hg concentrations (micrograms ⋅ grams−1, dw) in skipjack white muscle samples from the Pacific Ocean. The black dots represent the location of skipjack samples. Ocean areas correspond to the sample origin: NWPO, CNPO, NEPO, EPO, SWPO, and WCPO. The transparent dots represent the location of seawater samples with available and published MeHg data



Humans are exposed to toxic methylmercury mainly by consuming marine fish. New environmental policies under the Minamata Convention rely on a yet-poorly-known understanding of how mercury emissions translate into fish methylmercury levels. Here, we provide the first detailed map of mercury concentrations from skipjack tuna across the Pacific. Our study shows that the natural functioning of the global ocean has an important influence on tuna mercury concentrations, specifically in relation to the depth at which methylmercury concentrations peak in the water column. However, mercury inputs originating from anthropogenic sources are also detectable, leading to enhanced tuna mercury levels in the northwestern Pacific Ocean that cannot be explained solely by oceanic processes.



Anaïs Médieu, David Point, Takaaki Itai, Hélène Angot, Pearse J. Buchanan, Valérie Allain, Leanne Fuller, Shane Griffiths, David P. Gillikin, Jeroen E. Sonke, Lars-Eric Heimbürger-Boavida, Marie-Maëlle Desgranges, Christophe E. Menkes, Daniel J. Madigan, Pablo Brosset, Olivier Gauthier, Alessandro Tagliabue, Laurent Bopp, Anouk Verheyden, Anne Lorrain. Evidence that Pacific tuna mercury levels are driven by marine methylmercury production and anthropogenic inputs. Proceedings of the National Academy of Sciences Jan 2022, 119 (2) e2113032119; DOI: 10.1073/pnas.2113032119

Read the article on PNAS website

Franco-Quebec summer workshop on marine ecotoxicology

The IFQM is organising a new Summer School in Marine Ecotoxicology, this time in a hybrid format. It will take place from 14 to 17 July 2021, simultaneously at the IUEM and at the Universtité du Québec à Rimouski.

This high-level training course is intended for some thirty master’s level students registered at the Institute’s member institutions in France and Quebec. Among the speakers invited for the occasion, 3 are from LEMAR: Vianney Pichereau, Eric Deslandes and Michel Auffret.

More information and registration details are available on this page dedicated to the event on the IFQM website.

Download the training programme

ECOBIM network

Studying chemical contamination and its effects

Since 2004, the international French-speaking network ECOBIM has brought together about 120 people from 30 research teams in bilateral collaborative actions in the field of ecotoxicology of aquatic environments on 2 axes, trans-Atlantic and trans-Mediterranean. The Network also counts among its members actors from the economic and cultural world: aquaculture resource operators, parks, aquariums,…. Ecotoxicology must adapt to the changing context of environmental chemical contamination (new molecules, interactions with climate change, etc.) by developing new skills in environmental assessment tools and methods. The joint approach along the continuums is promoted, through work on all anthropized aquatic ecosystems: mainly rivers and large estuaries. This network also aims to contribute to academic training at doctoral and pre-doctoral level through a well-established presence of teams in European and North American universities, but also to contribute to informing the public about the environmental consequences of pollution.

The main objectives of the network are:

  • acquire scientific knowledge on new forms of chemical contamination by promoting a multidisciplinary approach between biologists and chemists
  • promote their application to the operational component of monitoring programmes, in particular by harmonising methods of data analysis and exploitation
  • develop relevant biological models for monitoring aquatic environments
  • promote in situ observation by organizing joint work on internationally important workshop sites
  • access shared analytical means and heavy experimental means


Institut Universitaire Européen de la Mer (France)  http://www-iuem.univ-brest.fr/fr

Université du Québec à Rimouski (Canada)  http://www.ismer.ca/

The ECOBIM Network in a few actions

– Coordination of bi-lateral research projects funded by: ANR, NSERC, OSPAR, Franco-Quebec Cooperation Programs,…

– Scientific animation

  • member mobility :stays of students, researchers, post-doctoral fellows
  • scientific meetings : methodological workshops (immunotoxicology, genotoxicology,…) since 2004 ; annual network facilitation conferences since 2006
  • multi-annual environmental assessment workshops on remarkable sites (St. Lawrence Maritime, Saguenay Fjord, Baie de Seine, Rade de Brest,…)

– Training through research : co-supervision of Master’s/Master’s students ; supervision of co-supervised doctorates

– Development of Digital Training Support


Europe: Pr Michel AUFFRET (Université de Brest, France, LEMAR)

North America: Pr Richard St LOUIS (UQAR, Qc, Canada)

ECOBIM’s webite

Ika Paul-Pont, CNRS Bronze medal 2019

With her colleagues from the PANORAMA team, and especially Arnaud HUVET, Ifremer researcher at LEMAR, their work on micro and nano-plastics is among the most cited in our laboratory.

Visit her page on Google Scholar.

See here her personnal page on our site to access her current projects, and click here to read her interview ‘in French) in IUEM’s letter of April 2019.

In 2018 her work was the subject of an article in Sciences-Ouest (in French also), in a special report on microplastics :

A Model of Mercury Distribution in Tuna from the Western and Central Pacific Ocean: Influence of Physiology, Ecology and Environmental Factors

Patrick Houssard, David Point, Laura Tremblay-Boyer, Valérie Allain, Heidi Pethybridge, Jeremy Masbou, Bridget E. Ferriss, Pascale A. Baya, Christelle Lagane, Christophe E. Menkes, Yves Letourneur, et Anne Lorrain



  • Information on ocean scale drivers of methylmercury levels and variability in tuna is scarce, yet crucial in the context of anthropogenic mercury (Hg) inputs and potential threats to human health. Here we assess Hg concentrations in three commercial tuna species (bigeye, yellowfin, and albacore, n = 1000) from the Western and Central Pacific Ocean (WCPO).
  • Models were developed to map regional Hg variance and understand the main drivers. Mercury concentrations are enriched in southern latitudes (10°S−20°S) relative to the equator (0°−10°S) for each species, with bigeye exhibiting the strongest spatial gradients. Fish size is the primary factor explaining Hg variance but physical oceanography also contributes, with higher Hg concentrations in regions exhibiting deeper thermoclines.
  • Tuna trophic position and oceanic primary productivity were of weaker importance. Predictive models perform well in the Central Equatorial Pacific and Hawaii, but underestimate Hg concentrations in the Eastern Pacific. A literature review from the global ocean indicates that size tends to govern tuna Hg concentrations, however regional information on vertical habitats, methylmercury production, and/or Hg inputs are needed to understand Hg distribution at a broader scale. Finally, this study establishes a geographical context of Hg levels to weigh the risks and benefits of tuna consumption in the WCPO.

Observed spatial variation in mercury concentrations (mg*kg −1 , dry weight) for bigeye, yellowfin, and albacore muscle samples captured in the Western and Central Pacific Ocean. Gray lines outline the five biogeochemical regions as defined in Houssard et al., 2017: NPTG (North Pacific Tropical Gyre), WARMm (Warm Pool modified), PEQD (Pacific Equatorial Divergence), SPSGm (South Pacific Subtropical Gyre modified) and ARCHm (Archipelagic deep basins modified) along with AUS-TAZ (Australia-Tasmania) and NZ (New Zealand).


Houssard, P., Point, D., Tremblay-Boyer, L., Allain, V., Pethybridge, H., Masbou, J., Ferriss, B.E., Baya, P.A., Lagane, C., Menkes, C.E., Letourneur, Y., and Lorrain, A. 2019. A Model of Mercury Distribution in Tuna from the Western and Central Pacific Ocean: Influence of Physiology, Ecology and Environmental Factors. Environmental Science & Technology. doi:10.1021/acs.est.8b06058.

Click here for the IRD news about this study (in French).

Tag Archive for: ecotoxicologie

Lucie TOUSSAINT thèse

Tag Archive for: ecotoxicologie