Motion adopted by LEMAR staff

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Les personnels CNRS/Ifremer/IRD/UBO du Laboratoire des sciences de l’environnement marin (LEMAR) soutiennent les initiatives qui se mettent en place au niveau mondial comme en France pour faire face à l’urgence planétaire (climat, biodiversité, environnement).

Nous demandons aux dirigeants politiques de tous bords d’unir leurs efforts pour mettre en œuvre des actions visant à abandonner la primauté des intérêts à court terme qui prévalent dans nos sociétés thermo-industrielles et qui conduisent à l’épuisement de nos ressources naturelles.

En particulier :

  • Nous soutenons les initiatives de la jeunesse mondiale pour faire de la journée du 15 mars 2019 une mobilisation d’envergure.
  • Nous appelons à participer à la marche mondiale pour le climat le 16 mars 2019.
  • Nous souscrivons aux différents appels des scientifiques (Appel de 300 chercheurs européens dans le quotidien Le Soir, Scientists warning de l’Alliance of World Scientists, tribune de 700 scientifiques français dans Libération, rapport du GIEC, etc.)* exigeant de la part des dirigeants politiques des actions concrètes et immédiates pour la protection de l’environnement.
  • Nous nous engageons à agir au quotidien pour réduire l’impact climatique et environnemental lié à nos activités de recherche.
  • Nous demandons instamment à nos institutions de tutelle (CNRS, Ifremer, IRD et UBO) de favoriser et d’accompagner nos démarches écoresponsables, et de s’engager publiquement et officiellement à prendre des mesures concrètes à la hauteur de l’urgence planétaire.

Faisons de 2019 l’année de la transition écologique !

Plouzané, le 12 mars 2019

*Appel de 300 chercheurs belges, français et suisses le 20 février 2019 :

Scientists warning de l’Alliance of World Scientists :

Appel de 700 scientifiques français le 8 septembre 2018 :

Rapport du GIEC (Groupe d’experts Intergouvernemental sur l’Evolution du Climat) publié le 8 octobre 2018 :




Effects of Omega 3 depletion on marine fish: ecophysiological approach

There is increasing evidence that climate change might critically deplete nutrients in food web of marine fish. In particular, a reduction in the production of Omega 3 (Ω3) in phytoplankton as a result of ocean warming can have negative impact on fish. Ω3 are fatty acids that are essential components of cell membranes. Such depletion in Ω3 in membranes can impair fish performance, however, the underlying mechanisms remain obscure. Mitochondria are likely to be involved in the fish response to Ω3 depletion. Changes in the composition of membrane fatty acid of mitochondria affect their efficiency. Organisms that have less efficient mitochondria are less able to maintain ATP [Adenosine TriPhosphate) production, a feature that is likely to affect the overall animal performance. This PhD work will therefore evaluate how the reduction in dietary Ω3 affect mitochondrial function and in turn the performance of a fish, the mullet (Liza aurata)

Thesis supervisor: José-Luis Zambonino-Infante

Thesis co-supervisor: Karine Salin

Read the terms and conditions and download the application form here:

Applications must be submitted before 30 June 2019, but we strongly encourage you to announce your intention to apply as soon as possible, by contacting the persons in charge of the subject.

Modeling reproductive traits of an invasive bivalve species under contrasting climate scenarios from 1960 to 2100

Mélaine Gourault, Sébastien Petton,Yoann Thomas, Laure Pecquerie, Gonçalo M. Marques, Christophe Cassou, Élodie Fleury,Yves-Marie Paulet et Stéphane Pouvreau


  • The DEB model available for the Pacific oyster was applied in a new coastal environment: the bay of Brest (France).
  • This version was successfully calibrated using a new dataset covering 6 years (from 2009 to 2014) of field monitoring.
  • The model successfully predicted in detail the complex reproductive processes of C. gigas, especially its spawning behavior.
  • Hindcasting and forecasting simulations of the reproductive phenology of C. gigas were performed using IPCC scenarios.


Identifying the drivers that control the reproductive success of a population is vital to forecasting the consequences of climate change in terms of distribution shift and population dynamics. In the present study, we aimed to improve our understanding of the environmental conditions that allowed the colonization of the Pacific oyster, Crassostrea gigas, in the Bay of Brest since its introduction in the 1960s. We also aimed to evaluate the potential consequences of future climate change on its reproductive success and further expansion.

Three reproductive traits were defined to study the success of the reproduction: the spawning occurrence, synchronicity among individuals and individual fecundity. We simulated these traits by applying an individual-based modeling approach using a Dynamic Energy Budget (DEB) model. First, the model was calibrated for C. gigas in the Bay of Brest using a 6-year monitoring dataset (2009–2014). Second, we reconstructed past temperature conditions since 1960 in order to run the model backwards (hindcasting analysis) and identified the emergence of conditions that favored increasing reproductive success. Third, we explored the regional consequences of two contrasting IPCC climate scenarios (RCP2.6 and RCP8.5) on the reproductive success of this species in the bay for the 2100 horizon (forecasting analysis). In both analyses, since phytoplankton concentration variations were, at that point, unknown in the past and unpredicted in the future, we made an initial assumption that our six years of observed phytoplankton concentrations were informative enough to represent “past and future possibilities” of phytoplankton dynamics in the Bay of Brest. Therefore, temperature is the variable that we modified under each forecasting and hindcasting runs.

The hindcasting simulations showed that the spawning events increased after 1995, which agrees with the observations made on C. gigas colonization. The forecasting simulations showed that under the warmer scenario (RCP8.5), reproductive success would be enhanced through two complementary mechanisms: more regular spawning each year and potentially precocious spawning resulting in a larval phase synchronized with the most favorable summer period. Our results evidenced that the spawning dates and synchronicity between individuals mainly relied on phytoplankton seasonal dynamics, and not on temperature as expected. Future research focused on phytoplankton dynamics under different climate change scenarios would greatly improve our ability to anticipate the reproductive success and population dynamics of this species and other similar invertebrates.

Figure 4: Oyster growth and spawning simulations obtained by the DEB model compared with observed data from 2009 to 2014 (DFM = Dry Flesh Mass). Observed DFM is represented by black dots with standard deviation bars (n = 30). Grey lines represent individual growth trajectories simulated by the model. The dark red bold line represents the mean of the 30 trajectories.


Gourault, M., Petton, S., Thomas, Y., Pecquerie, L., Marques, G.M., Cassou, C., Fleury, E., Paulet, Y.-M., & Pouvreau, S. 2019. Modeling reproductive traits of an invasive bivalve species under contrasting climate scenarios from 1960 to 2100. Journal of Sea Research 143: 128–139. doi:10.1016/j.seares.2018.05.005.

Click for the journal page.

On 17/12/2018 at 3pm in lecture hall A of IUEM, thesis defence of Pierre Poitevin (LEMAR)

Title: Sclerochronological approaches in Saint-Pierre & Miquelon: from sub-hourly to multidecadal environmental reconstructions

The panel will be composed of:

  • Anne Lorrain (Examiner) IRD / LEMAR
    Claire Lazareth (Examiner) IRD / LOCEAN
    Stéphanie Thièbault (Examiner) CNRS / Director of INEE
    Philippe Archambault (Rapporteur) Univ. Laval
    Matthieu Carré (Rapporteur) CNRS / LOCEAN

Thesis supervisors:

  • Laurent Chauvaud and Pascal Lazure

Summary :

Coastal ecosystems are exposed to global climate change leading to modifications of their structure and functioning. However, little is known about the variability of their physical properties before 1950, mainly because of the lack of long-term instrumental measurements. The hard parts of long-lived marine biota hold the potential to extend instrumentally derived observations, at different temporal and spatial resolutions, in order to enhance our understanding of past environmental processes.

This PhD dissertation takes place on Saint-Pierre & Miquelon (SPM), a small archipelago at the confluence of major oceanic currents marking the boundary between the North Atlantic Ocean subtropical and subpolar gyres. In addition to its global key position, the abrupt bathymetric change occurring in the North West of Miquelon Island generates the anti-cyclonic propagation of a tidal coastal trapped wave around this archipelago. This local phenomenon, leads during the stratified period to the largest (up to 11.5°C amplitude) daily (25.8 h) temperature oscillations ever observed-at any frequency-on a stratified mid latitude continental shelf.

This work is based on the analyses of local marine biota hard parts to gain insights about past environmental variability at these two scales. First, I have learned different sclerochronological methods through Spisula solidissima study. Global and multi-decadal time scales were reached using the longest lived bivalve known to date Arctica islandica, and Clathromorphum compactum a newly discovered long-lived coralline alga. The relationships observed at SPM between A. islandica and C. compactum sclerochronological records and different geographical scales environmental datasets yield details about past large-scale oceanographic variability and ecosystem dynamics. Local, high-frequency (25.8 h) temperature oscillations were tracked using sclerochronological information contained in Placopecten magellanicus a fast growing (ca. 500 µm / day) bivalve species.

This study points out the relevant position of this archipelago for studying multiple scale oceanographic variability, biological responses and ecosystem dynamics facing global changes.

Biological invasions


The ecological impacts of aquatic invasive species are a growing concern for coastal zone management and conservation. The French Channel-Atlantic coasts are no exception, mainly because of international shipping practices and aquaculture. France is even the European country most colonized by introduced species of macroalgae. The cost-benefit analysis of invasion management is not straightforward, even though the exploitation of several living resources is based on the invasive characteristics of these species (for example, molluscs and macrophytes in aquaculture). The oyster Crassostrea gigas is considered a nuisance species in the Wadden Sea or Australia, where it supplants native oysters, while it is the subject of a major exploitation in France at the same time. In addition, there are many historical cases showing that an invasion initially “under control” is not necessarily permanent, even after several decades. Understanding the interactions between human activities, the functioning of ecosystems and global change is therefore essential in order to establish new management options. New approaches need to be developed to prevent any inadvertent introduction and limit the side effects of ongoing invasions.

The impacts of the ongoing global changes are not conducive to optimism. Thus, the French Atlantic coast is confronted with at least three major environmental changes:

● the average annual temperature of seawater is rising steadily (about 1.5 ° C over the past 25 years),

● there is a very clear positive trend of the North Atlantic Oscillation (NAO),

● there is a drastic decrease in freshwater inputs due to climate change and concomitant changes in human activities on watersheds (eg increased irrigation for agriculture). The “marinating” of estuaries near ports leads to an increase in the potential risks of invasion by new marine species, while global warming favors the establishment of subtropical exotic species (for example the harmful dinoflagellates of the genera Ostreopsis and Gambierdiscus in the Bay of Biscay). By definition, species invaders are able to adapt to their new environment and are best placed to cope with global changes. What about native species that are not used to such environmental changes? Although climate change is progressive, will all species (native and invasive) adapt or will we observe a global homogenization of flora and fauna?


Quemeneur Jean-Baptiste thèse