The Anthropocene marks a new era where human activities profoundly impact the Earth’s climate and ecosystems, driven by the unprecedented release of CO₂ into the atmosphere (Crutzen and Stoermer, 2000; Zeebe et al., 2016). The ocean plays a crucial buffering role, absorbing approximately 90% of the excess heat and about a quarter of anthropogenic CO₂ emissions annually (Hoegh-Guldberg et al., 2014; Le Quéré et al., 2018; Friedlingstein et al., 2025). However, this comes at a cost: increasing sea surface temperatures (Gleckler et al., 2012), altered ocean circulation, intensified stratification affecting primary production (Li et al., 2020), declining pH (ocean acidification), and reduced oxygen availability (Gattuso and Hansson, 2011; Pörtner et al., 2014).
Calcifying organisms are particularly vulnerable to these changes, as they rely on sufficient carbonate ion concentrations for shell formation, making them susceptible to dissolution under decreasing pH conditions (Riebesell et al., 2000; Gangstø et al., 2011). Among these, planktonic foraminifera, single-celled calcifying microzooplankton, play a key role in the marine carbon cycle and provide critical insights into past climate conditions through their extensive fossil record. Understanding their ability to adapt to rapid and extreme environmental changes is essential for predicting future ocean ecosystem dynamics. If planktonic foraminifera have been extensively studied in deep-sea sediments (e.g. ForCens, Siccha et al., 2017), in sediment traps (eg., Jonkers et al., 2019), or in plankton nets (e.g. FORCIS, Chaabane et al, 2024); to date, planktonic foraminifera sensitivity to environmental changes have been seldomly studied using experimental schemes. This is because until recently it was impossible to maintain them over multiple generations in culture conditions (Schiebel and Hemleben 2017). This has changed (Meilland et al., 2023; 2024) and it is now possible to obtain reproduction and grow foraminifera offspring (hundreds) entirely and over multiple generations in the laboratory. Based on these findings and expertise, a unique “continuous planktonic foraminifera” facility has started at CEREGE in February 2025, opening unique and new perspectives such as the hereby proposed research thesis.
This PhD project will investigate how planktonic foraminifera respond to climate change by analyzing their morphology, physiology, and population dynamics in two highly sensitive yet contrasting regions: the Arctic and the Mediterranean Sea. The Mediterranean is experiencing warming, deoxygenation, and acidification (e.g. Sugie et al., 2020; Reale et al., 2022), while the Arctic is undergoing rapid ice melt and freshwater influx, dramatically changing salinity.
In both regions, species of foraminifera from the same genus can be encountered, giving us the possibility to assess their adaptability and plasticity under contrasted environments (polar vs. temperate to subtropical conditions) and different climate stressors.
Using a combination of novel laboratory culturing techniques setup at CEREGE, automated imaging of foraminifera in the platform MicroAutomate at CEREGE using the different high throughput imaging and processing setups including MiSo (MicroFossil Sorter), SASHIMI and TRAIT, and field data from long-term sediment trap time-series (e.g., SNO MOOSE in the Mediterranean), this research will examine foraminiferal adaptation in the very recent past (sediment traps) and under controlled future climate scenarios (experiments).
The project will focus on two primary objectives:
1. Tracking long-term changes in planktonic foraminifera assemblages and shell morphometrics (weight and size) using Mediterranean sediment trap samples (SNO MOOSE) and Arctic plankton samples collected over the past decade. In the Mediterranean Sea, the PhD applicant will focus on the “Planier” time-series (collaboration with Xavier Durrieu de Madron, Univ. Perpignan). In the Arctic, the PhD applicant will analyze samples collected at a repeated station in the Barents Sea for the past decade (collaboration with Mohamed Ezat, IC3, UiT, the Arctic University of Norway, Tromsø). If the project goes at a rapid pace, samples from the mooring “Lion” from the SNO MOOSE and from the Hausgarten area (Fram Strait) will be added.
2. Conducting continuous laboratory culture experiments on two selected species from each environments (Mediterranean Sea and the Arctic) belonging to the same genus (Neogloboquadrinida and Globigerina – for which the PI already has a record of successful culture experience) if not directly species, exposing them to extreme conditions of pH, salinity, and temperature to assess their tolerance and adaptation mechanisms.
Primary expected outcomes of the PhD research
• A comprehensive assessment of how planktonic foraminifera populations have already responded to climate change in two contrasting oceanic regions.
• Experimental evidence of species-specific adaptation mechanisms to future climate conditions.
• State-of-the-art multigenerational culture work with planktonic foraminifera from different species.
Candidate Profile & Training
The PhD project will provide training in:
• Plankton sample collection and processing techniques.
• Laboratory culture work and experimental design for marine organisms.
• AI-assisted microscopy and large-scale dataset analysis.
The candidate should have experience or strong interest in microscopy techniques, biological oceanography, ecology, and environmental chemistry. Skills in data analysis and programming (e.g., R, Python) are a plus.
This project will contribute to the establishment of a unique continuous planktonic foraminifera culture facility in France, fostering interdisciplinary collaboration between marine biologists, paleoceanographers, and climate modelers. The findings will advance our understanding of microzooplankton responses to climate change and improve projections of marine ecosystem stability in the Anthropocene.
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