Student Ambre Chabert, Master 2 IMBRSea
from 01/04/2021 au 06/30/2021
supervisor : Stéphane Hourdez

General information :

Deep-sea hydrothermal communities are host to a relatively small number of very specialized taxa that are only found near active hydrothermal vents. Community composition varies among biogeographic provinces in the world. In the West Pacific, the complex geological history has led to similar-looking communities amongst different regions. The goal of this research line is to use molecular barcode approaches (a fragment of mitochondrial CoxI gene) to compare the species composition of each community, determine whether larval exchange takes place (connectivity) and whether our estimation of biodiversity is skewed by the presence of cryptic species.

These data will have important repercussions in our understanding and in the management and conservation of these unique ecosystems and the species that inhabit them. This is especially important in the West Pacific, where deep-sea mining is planned in the upcoming years. The produced data will be made accessible on public databases such as GenBank use by other researchers in the world. 

Stage de M2

Scientific supervisor: GUIZIEN Katell
, DR2 HDR CNRS (Tel : 04 68 88 73 19, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.),

Hosting laboratory: Laboratoire d’Ecogéochimie des Environnements Benthiques (UMR8222), Observatoire Océanologique de Banyuls S/ Mer, 1 avenue Pierre Fabre, 66650 Banyuls S/ Mer, France

Short description of the internship:

When ocean beds are covered by large obstacles, the classical boundary layer structure is significantly modified. The wakes produced by these obstacles create strong spatial variations in the flow, over a region (embedded within the boundary layer) known as the roughness sublayer (Ghisalberti 2009). Long-lived hard and soft coral species that are able to develop dense patches with a complex, three-dimensional structure form an animal forest canopy (sensu Rossi et al 2017), similar to trees in terrestrial systems (Ghisalberti and Nepf, 2002). Aside from the shelter provided by this canopy to other organisms, the animal forest can significantly modify the local physical and biogeochemical environment (reviewed in Guizien and Ghisalberti, 2017). Flow velocity profiles were measured with a high-resolution Doppler profiler across the 2 meters above the bottom in locations covered by soft corals at differents population densities. In shallow locations, the flow was dominated by waves (oscillatory flow) and in deep locations, by current (steady flow). The objective of the internship is to analyse the near-bottom flow velocity profile measurements with various signal processing methods developping customed Matlab routines in order to quantify the animal forest canopy effect on the flow (steady and unsteady) and test wether it can be related to any animal forest descriptors (height, population density). In the case of steady flows, canopy descriptors as established for atmospherical urban canopies will be considered (Mac Donald, 2000).

Facilities for the intern:
Computing facilities and Matlab software.

Bibliographical references:

  • Mac Donald RW. Modelling the mean velocity profile in the urban canopy layer. Boundary Layer Meteorology 2000 ; 97:25-45.
  • Ghisalberti M Obstructed shear flows: similarities across systems and scales. J. Fluid Mech. 2009 ; 641:51-61.
  • Ghisalberti M, Nepf H. The structure of the shear layer in flows over a rigid and flexible canopies. J. Geophys. Res. Oceans. 2002 ; 107(C2): 3011-1-11.
  • Guizien K., Ghisalberti M. (2017) Living in the Canopy of the Animal forest: Physical and Chemical Aspects. In Marine Animal Forests. The Ecology of Benthic Biodiversity Hotspots. S. Rossi, L. Bramanti, A. Gori, C. Orejas Saco del Valle (Eds) . Springer. ISBN: 978-3-319-17001-5 (Online).
  • Rossi S, Bramanti L, Gori A, Orejas C. (2017) An Overview of the Animal Forests of the World. In Marine Animal Forests. The Ecology of Benthic Biodiversity Hotspots. S. Rossi, L. Bramanti, A. Gori, C. Orejas Saco del Valle (Eds) . Springer. ISBN: 978-3-319-17001-5 (Online).

PhD student : Claudia MATURANA (2019-2021)

Supervisor (ASR):
Pierre Galand (LECOB)
Co-supervisor: Camila Fernandez (LOMIC)

General information:
The southern Patagonia of Chile concentrates one of the largest reserves of fresh water in the world, which makes it a key region for the development of anthropogenic and productive activities. The coast of the Antarctic Peninsula is characterized by being very vulnerable to climate change and being an area of ​​high biodiversity and biomass production, presenting diverse and complex ecosystems that harbor rich marine communities controlled by local and regional oceanographic processes. For the sub-Antarctic and Antarctic zones, a decrease in ice cover is predicted, which will affect the marine and coastal systems, transforming its structure and altering the dominant species, their functioning and productivity levels. Regarding the structure of bacterial communities in bodies of waters of high latitudes with the entrance of fresh water from glaciers, different studies have reported presence of the three domains of life Bacteria, Archaea and Eukarya. Studies carried out in fjords of the southern Patagonia of Chile, suggest that the melting of glaciers would favour the development of microorganisms adapted to cold and low salinity during a scenario of high discharge, generating in this way changes in the structure of the normal microbial community and possible changes in the trophic web.

The Yendegaia fjord is characterized for being a low nutrient system and for presenting l

PhD student: Elise VISSENAEKENS (2019-2021)

Supervisor (ASR): Katell Guizien

General information:
Ecological connectivity is an emerging property of ecosystems that allows the maintenance and dissemination of species within a biogeographic region and the resilience of their populations to local disturbances. This ecological connectivity occurs for most marine species by dispersal of the larval stage by currents and currently studied by two approaches, by the analysis of population genetics and by the biophysical simulation of larval transport (Guizien et al., 2006 ; 2012). The latter approach makes it possible to explore the potential ecological connectivity between existing populations, such as genetic methods, but also to or from potential habitats that a species could colonize in a changing context. Thus, the biophysical simulation approach of ecological connectivity is of major interest for maritime spatial planning due to its ability to anticipate changes in the distribution of habitats in the current context of ocean circulation but also in the context of its future development.
A prerequisite for the biophysical simulation of ecological connectivity is to rely on simulations of reliable marine circulation at spatial and temporal scales influencing the connectivity of populations. For spatial scales, this involves describing the currents at scales of around one hundred meters around populations to properly describe retention and at hundreds of kilometers to describe the connections between populations. For the time scales, it is a question of taking into account the meteorological variability, the episodes of reproduction being often fleeting. The SYMPHONIE model makes it possible, thanks to a curvilinear dipolar grid, to carry out such simulations but it is now necessary to validate them. The objective of this thesis is to establish validated reference simulations of high-resolution circulation, along the coasts and in the canyons of the Gulf of Lions, in the current and future context. The first step will be to evaluate, in the face of current observations, the reliability of simulations carried out in the Gulf of Lion on a curvilinear grid (Briton et al., in press; resolution of 80 m around Cap de Creus and 2.7 km above the abyssal plain) over the period 2009-2013. All the current data available (SAVED database, CASCADE campaigns, CRUMED mooring, campaigns
LATEX) will be used for this evaluation. The second step will consist in carrying out simulations for the period 2090-2095 on the same spatial model and using the same climatic forcings as those used by Hermann et al. (2008) for a future regional simulation in the Gulf of Lion. The evaluation of the impact of the spatial resolution will be made by comparison with this regional simulation.
PhD student: Sylvain BLOUET  (2018-2020)

 

Supervisor (ASR): Katell Guizien (LECOB)
Co-supervisor (ASR): Anne Chenuil (IMBE)

Funding: agence de l'eau