Le jeudi 20 novembre 2025, Arnaud BOULENGER présentera l'examen en vue de l’obtention du grade académique de Docteur en Sciences (Collège de doctorat en Océanographie) sous la direction de Sylvie GOBERT et Eric GOBERVILLE.
Cette épreuve consistera en la défense publique d’une dissertation intitulée :
« Multi-scale assessment of the biological and ecological responses of Posidonia oceanica to transplantation for the optimization of seagrass meadow restoration ».
Le Jury sera composé de :
Mme A. ALVERA-AZCARATE (Présidente), Mmes et MM. M. CANNAC-PADOVANI (Office de l’Environnement de la Corse), J. DETER (Université de Montpellier), S. GOBERT (Promotrice), E. GOBERVILLE (Université de la Sorbonne) (Co-promoteur), M. MARENGO (STARESO), M. MONTEFALCONE (Università degli Studi di Genova), S. ROBERTY (Secrétaire).
The restoration of coastal ecosystems is now considered a priority to support the recovery of their ecosystem services. In the Mediterranean Sea, numerous projects have been carried out over the past decades to restore the endemic Posidonia oceanica (L.) Delile meadows. However, major knowledge gaps remain regarding the transplantation of this species, particularly with respect to the performance of different anchoring techniques and donor sources. This thesis aimed to assess the relative efficiency of three transplantation methods using biodegradable materials and to evaluate the performance of two donor sources: naturally detached fragments drifting on the seafloor (i.e., storm-fragments) and cuttings harvested from donor meadows. To address these objectives, a three-year monitoring program was conducted in Calvi Bay (Corsica, France), where 693 cuttings were transplanted onto dead matte using three transplantation techniques: individual fixation (iron staples), soft three-dimensional structures (coconut fiber mats), and rigid three-dimensional structures (BESE elements). The performance of these transplantation methods and donor sources was evaluated based on survival rate, cost–benefit ratio, and the morphological, microbiological, physiological, and biochemical dynamics of transplants compared with reference meadows.
Individual fixation methods showed an excellent cost–benefit ratio but were suitable only in low-hydrodynamic areas with minimally degraded dead matte. Rigid three-dimensional structures were more expensive but achieved high survival rates in high-hydrodynamic environments. Methods allowing direct contact between transplants and the matte promoted root system development and the establishment of bacterial communities resembling those of natural meadows. Storm-fragments performed similarly to donor cuttings in terms of survival, leaf and root morphology. However, donor cuttings displayed root microbiome structure as well as physiological and biochemical traits more similar to natural meadows than storm-fragments two years after transplantation. Physiological and biochemical differences between the two donor sources diminished after two years, suggesting that donor cuttings outperform storm-fragments during the first two years following transplantation. This thesis provides key insights into major research and development issues related to the transplantation of P. oceanica meadows.
La thèse est intitulée : « Impact of bathymetric thresholds on the hydrodynamic circulation in a micro-tidal setting and on the sedimentary processes in a semi-enclosed basin : case of the Corinth Gulf (Greece) ».
La thèse est intitulée : « Multiscale hydrodynamic modelling of the Danube Delta ».
La thèse est intitulée : « Emissions of CO2, CH4, and N2O from urban ponds of the city of Brussels ».
La thèse est intitulée : « Unveiling the Ecological Strategies of Streptomyces scabiei: Virulence, Competition and Nutrient Adaptation ».
La thèse est intitulée : « Formations des futurs aménageurs et relations praticiens - mandataires publics: conception et implémentation d'un module de formation ».
La thèse est intitulée : « Probing Protein Folding Pathways by Hydrogen-Deuterium Exchange. A Time-Resolved Study of BS3 ß-Lactamase as a Model System ».
