Phd Thesis Defense of Mathisse Meyneng

Mathisse Meyneng , doctoral student in the Pelagic Ecology laboratory of the Coastal Ecosystem Dynamics unit, will defend his thesis on Thursday 12 December 2024 at 9:30 am at the IUEM in Plouzané (amphitheatre A)

The microbiome at the land-sea interface: Influence of variable river inputs in shaping coastal communities from daily to pluri-secular scales

This thesis focuses on the study of the land-sea continuum and in particular the analysis of river impacts on the spatio-temporal variability of microbial communities in the coastal ecosystem. The association between changes in the structure of these communities, assessed by environmental DNA sequencing, and different physical, chemical, biological and biogeochemical parameters has made it possible to better understand the dynamics of coastal ecosystems in the face of natural and human disturbances on variable time scales and space. New Caledonia, with its subtropical climate, with contrasting seasons, its soils rich in metals, and specific human pressures, was chosen as a natural laboratory to study variable river impacts. The results reveal that the influence of natural factors such as cyclones and watershed geology generate specific microbial communities that could be used as tracers of these impacts and demonstrate strong connectivity between terrestrial landscapes and coastal ecosystem. Human activity exacerbates this link. The centuries-old exploitation of a nickel mine has shown that modifications in the composition and quantity of sediment inputs due to mining activity have generated hitherto invariant changes in microbial communities. This thesis combines multi-scale and multidisciplinary approaches to develop a holistic vision of the coastal ecosystem with its link with the land. The results promote the establishment of management and conservation systems for these fragile ecosystems in the face of increasing anthropogenic and natural pressures.

Jury :

  • Tristan CORDIER - Senior researcher, Norwegian Research Centre NORCE
  • Anders LANZÉN - Senior investigator, Centro de Investigación Marina y Alimentaria AZTI
  • Flora VINCENT - Group leader, European Molecular Biology Laboratory EMBL   
  • Gaëtan BURGAUD - Maître de conférences, Université Bretagne Occidentale, LUBEM
  • Nathalie SIMON  - Maître de conférences, Sorbonne Université
  • Philippe PONDAVEN - Professeur des Universités, LEMAR
  • Dir. de thèse : Raffaele SIANO - Cadre de recherche - HDR, Ifremer DYNECO
  • Co-dir. de thèse : Hugues LEMONNIER - Cadre de recherche - HDR, Ifremer LEAD, UMR ENTROPIE, New Caledonia