PhD : Impacts of chemical contaminants on the holobiont of harmful microalgae (M/F)

Closure date for receipt of applications: 20/07/2025 This thesis is based on strong interactions between several research units specialising in the chemical contamination of the environment, the ecology of coastal ecosystems and the microbiology and physiology of microalgae. You will be based in the PHYTOX unit, whose main objectives are to gain a better understanding of the physiology of toxic and harmful microalgae (mainly cyanobacteria, diatoms, dinoflagellates and haptophytes) and to understand the diversity, role and fate of the toxins produced. Unit website: You will interact with (i) the CCEM unit, which develops scientific knowledge on the transfer and biological effects of chemical contaminants in marine ecosystems. CCEM's research enriches the expertise in Public Policy Support and makes it possible to assess the chemical pressure on marine ecosystems (Unit site: (ii) the COAST unit, comprising nine Environment Resource Laboratories (LER) and a data management and development laboratory, spread over fourteen sites covering the entire coastline of mainland France. The main missions of these laboratories are coastal observation (monitoring networks and diagnostics of the quality of the marine environment) and the study of coastal and shellfish farming ecosystems (unit website: and (iii) the MASAE unit, more specifically the EM3B laboratory, which studies marine bacterial communities and innovation opportunities for biotechnologies and the bio-economy. What is the subject of the thesis ? Algal blooms are sudden, natural and recurrent blooms of toxic and non-toxic phytoplankton species that can seriously affect ocean biodiversity, human health, coastal socio-economics and food security. The study of these blooms has rarely taken into account the multiple interactions that occur in the phycosphere, either between microalgae and bacteria, or between bacteria. Another important issue that is still neglected is the influence of chemical contamination on algal blooms. Among the species that form blooms, Lepidodinium chlorophorum is a Dinoflagellate known for producing coloured water events in coastal environments, leading to mass mortalities of marine organisms through the production of large quantities of extracellular compounds, grouped together under the term extracellular matrix. Consequently, the algal holobiont (which includes the algal cell, the components of the extracellular matrix and the associated bacteria) must be considered in its entirety. However, the mechanisms involved in the response of the holobiont of harmful microalgae to pollutants and the consequences for the appearance, severity and persistence of algal blooms are, to date, little known and require integrative studies to better understand the dynamics of blooms, their ability to develop in an increasingly polluted environment and their ecological impact. Your mission The objectives are to study the interactions between the dinoflagellate L. chlorophorum, its extracellular matrix and its bacterial consortia during a coloured water event and to estimate the potential role of this matrix in the retention/concentration of pollutants. These data will be acquired (i) in the field during sampling campaigns planned in various projects aimed at characterising phytoplankton and bacterial communities, as well as physico-chemical parameters before, during and after these blooms and (ii) in the laboratory under controlled conditions where cultures of microalgae associated with different synthetic microbial communities will be exposed to pollutants in order to study their physiology and the components of the extracellular matrix produced This thesis proposes to combine laboratory and field analyses: chemical analyses will be used to describe the pollutants present in the environment. Molecular biology will highlight the taxonomic, metabolic and functional complexity of microbial populations and their responses to pollutants. Finally, biochemical analyses will be used to analyse the composition of the extracellular matrix. The integration of all these data will provide an overview of the effects of pollutants and help to understand some of the determinants of the dynamics of algal blooms. How are your activities organised?

• Full Time
• Regular fieldwork
• Presentation of results and discussions in France and abroad

What are your benefits?

• Phd is a real opportunity to work on Ifremer's scientific and technological priority themes. It entitle the holder to a gross monthly salary of 2300 euros gross for a period of 3 years, which cannot be combined with other scholarships.
• We have a teleworking agreement and our staff have 12 comp time days and supra statutory leave.
• We allocate a significant budget to developing skills, through individual or collective training actions.
• We have a CSR policy inspired by the purposes of the institute (sustainable mobility allowance, etc.)

How to apply for this position? Your application file must include:

• a curriculum vitae
• a covering letter
• a reference letter
• an academic transcript (Bachelor + Master 1 and first semester Master 2)

Your application must be compiled into 1 PDF files. The deadline for applications is July 20th, 2025. Nevertheless, we strongly urge you to let us know as soon as possible of your intention to apply, by contacting the subject supervisor: Anthony Bertucci In parallel, please submit your application to the doctoral school: ED642 VAAME Doctoral students' contracts will start as of October 6th, 2025, subject to the submission of administrative documents authorizing Ifremer to recruit the doctoral student (certificate of completion of the Master 2 or engineering degree + visa for foreign doctoral students outside the EU). What are the next steps? Application on the Ifremer job website and on the Amethis website of the ED VAAME Who are you : - Graduate student (M.Sc.) in phytoplankton and microbial ecology, molecular biology, or related fields. You have the following skills, knowledge and experience:

• Good knowledge of bioinformatics tools and R software.
• Knowledge of molecular biology practices in the laboratory.
• Ability to design an experimental plan.
• Very good ability to combine laboratory and field work and data processing.
• Good level of English.

You have the following qualities:

• Good organisational skills, thoroughness, curiosity and initiative.
• Interest in interdisciplinarity
• Autonomy
• Ability to communicate and work as part of a team