Study on the microalga Phaeocystis and its symbiotic life

The microalga Phaeocystis is a key ecosystem engineer, significantly influencing climate-active gases, carbon cycling, food web structure, and nutrient dynamics in Arctic and Antarctic marine environments. As the Arctic continues to warm and ocean stratification intensifies, Phaeocystis species are expected to become more dominant. This microalga is also known to thrive in the plankton during the polar night and to typically form massive blooms at spring. Yet, genetic diversity of arctic Phaeocystis remains largely unknown, as well as the morphological and physiological plasticity. Acclimatization strategy in fluctuating conditions, including the capacity to thrive in the polar night, has not been addressed so far in the arctic species. In the ocean, many planktonic species depend on the microalga Phaeocystis, not only grazers (microzooplankton), but also host organisms that strictly depend on Phaeocystis as symbionts. These cellular interactions remain unknown in the Arctic region.

Therefore, the overall aim of this project is to improve our knowledge of the biology and physiology of Phaeocystis species in the Arctic. We will investigate its genetic diversity, cell biology, potential symbiotic interactions and its morpho-physiological plasticity in different conditions, including darkness. We also aim to unveil whether Phaeocystis can be a symbiont in diverse hosts, such as acantharians and dinoflagellates. Our ambition is to provide solid knowledge and reference data for the Arctic Phaeocystis species. New cultures, and genomics and imaging datasets will represent fundamental reference resources for future polar expeditions (e.g. Tara Polar Station), which is pivotal information to fully understand and predict the biology and adaptive capacity of Phaeocystis in the Arctic region.