Number of documents


Mélilotus Thyssen Marine microbial Ecologist and Biogeochemist

I am a marine microbiologist and biogeochemist, dealing with the multiparametric complexity of the ocean and the microorganisms floating inside.I am looking at the very small scales related to phytoplankton organisms, as far as we can. Meaning I study all together their functional diversity (regarding their role in biogeochemical processes), their structural diversity (how the functional groups or species are making a community), and most of all, the dynamical behavior of each entity within the community (hourly to daily physiological changes and abundances variations), surrounded by water in motion.
The use of high resolution automated sensors capable of precise single cell observation that can give insight to phytoplankton functional and structural heterogeneity within spatial and temporal variability is part of my job. I use automated flow cytometry in combination with several sensors deciphering the surrounding chemical and physical conditions.

I am singularly looking into the very fast reactivity of the smallest phytoplankton size classes (pico-nanophytoplankton) after drastic environmental changes (as an example, after the upper layer mixing linked to strong winds), especially in the oligotrophic regions where low productivity is expected.

I also collect basin scale high resolution phytoplankton distribution to understand large scale seasonal changes in hydrological properties affecting phytoplankton community structure and spatial heterogeneity. From the tiny single cell observation at high resolution (km scale/hourly scale) to the large scale observation increases datasets quality and our potential of undertanding. Combination with remote sensing (PHYSAT for example) and modelling will increase the sensitivity of extrapolation and sharpen our understanding.

Journal articles12 documents

  • Pierre Marrec, Gérald Grégori, Andrea M. Doglioli, Mathilde Dugenne, Alice Della Penna, et al.. Coupling physics and biogeochemistry thanks to high-resolution observations of the phytoplankton community structure in the northwestern Mediterranean Sea. Biogeosciences, European Geosciences Union, 2018, 15 (5), pp.1579 - 1606. ⟨10.5194/bg-15-1579-2018⟩. ⟨hal-01735426⟩
  • R. Leroux, Gérald Grégori, F. Carlotti, Karine Leblanc, Melilotus Thyssen, et al.. Combining laser diffraction, flow cytometry and optical microscopy to characterize a nanophytoplankton bloom in the Northwestern Mediterranean. Progress in Oceanography, Elsevier, 2018, 163, pp.248-259. ⟨10.1016/j.pocean.2017.10.010⟩. ⟨hal-01638096⟩
  • Melilotus Thyssen, Gérald Grégori, Jean-Michel Grisoni, Maria-Luiza Pedrotti, Laure Mousseau, et al.. Onset of the spring bloom in the northwestern Mediterranean Sea: influence of environmental pulse events on the in situ hourly-scale dynamics of the phytoplankton community structure. Frontiers in Microbiology, Frontiers Media, 2014, 5, pp.387. ⟨10.3389/fmicb.2014.00387⟩. ⟨hal-01321252⟩
  • Anthony Malkassian, David Nérini, M. A. Van Dijk, Melilotus Thyssen, Claude Manté, et al.. Functional Analysis and Classification of Phytoplankton Based on data from an Automated Flow Cytometer. Cytometry Part A, Wiley, 2011, 79A, pp.263-275. 〈10.1002/cyto.a.21035〉. 〈hal-00579516〉
  • Nicole Garcia, Michel Denis, Melilotus Thyssen, Beatriz Beker, Dilek Ediger, et al.. Phytoplankton distribution during two contrasted summers in a Mediterranean harbour: combining automated submersible flow cytometry with conventional techniques. Environmental Monitoring and Assessment, Springer Verlag (Germany), 2010, pp.1-16. ⟨hal-01663229⟩
  • Michel Denis, Melilotus Thyssen, V. Martin, B. Manca, F. Vidussi. Ultraphytoplankton basin-scale distribution in the eastern Mediterranean Sea in winter : link to hydrodynamism and nutrients. Biogeosciences, European Geosciences Union, 2010, 7, pp.2227-2244. ⟨10.5194/bg-7-2227-2010⟩. ⟨hal-00514544⟩
  • Melilotus Thyssen, Delphine Mathieu, Nicole Garcia, Michel Denis. Short-term vaiation of phytoplankton assemblages in Mediterranean coastal waters recorded with an automated submerged flow cytometer. Journal of Plankton Research, Oxford University Press (OUP), 2009, 30 (9), pp.1027-1040. ⟨10.1093/plankt/fbn054⟩. ⟨hal-00363507⟩
  • Hera Karayanni, Urania Christaki, France Van Wambeke, Melilotus Thyssen, Michel Denis. Heterotrophic nanoflagellate and ciliate bacterivorous activity and growth in the northeast Atlantic Ocean : a seasonal mesoscale study. Aquatic Microbial Ecology, Inter Research, 2008, 51, pp.169-181. ⟨10.3354/ame01181⟩. ⟨hal-00290748⟩
  • Samer Sakr, Melilotus Thyssen, Michel Denis, Cheng-Cai Zhang. Relationship among Several Key Cell Cycle Events in the Developmental Cyanobacterium Anabaena sp. Strain PCC 7120. Journal of Bacteriology, American Society for Microbiology, 2006, 188/16, pp.5958-5965. ⟨hal-00092841⟩
  • Gaetan Gogniat, Melilotus Thyssen, Michel Denis, Cesar Pulgarin, Sam Dukan. The bactericidal effect of TiO2 photocatalysis involves adsorption onto catalyst and the loss of membrane integrity. FEMS Microbiology Letters, Wiley-Blackwell, 2006, 258, pp.18-24. ⟨hal-00092800⟩
  • Anne Maixandeau, Dominique Lefèvre, Hera Karayanni, Urania Christaki, France Van Wambeke, et al.. Microbial community production, respiration and structure of the microbial food web of an ecosystem in the northeastern Atlantic Ocean. Journal of Geophysical Research, American Geophysical Union, 2005, 110, pp.C07S17 -13. ⟨hal-00092669⟩
  • Melilotus Thyssen, Dominique Lefèvre, Guy Caniaux, Josephine Ras, Camila I. Fernandez, et al.. Spatial distribution of heterotrophic bacteria in the northeast Atlantic (POMME study area) during spring 2001. Journal of Geophysical Research, American Geophysical Union, 2005, 110, pp.C07S16-16. ⟨hal-00092675⟩