Prokaryote-phytoplankton interactions in Antarctic ice sheet melting environments: the key role of iron

The accelerated melting of the Antarctic ice sheet due to global warming profoundly influences adjacent marine ecosystems. The delivery of fresh water from the ice sheet potentially represents a new source of key nutrients, including iron (Fe), a micronutrient known to limit phytoplankton primary production and the biological pump of CO2 in the Southern Ocean. But the bioavailability of Fe, provided mainly in the form of colloids and particles by glacial ice, is poorly understood. The main objectives of PIANO are to elucidate the role of marine bacteria as key engineers in the transformation of Fe delivered by Antarctic ice sheet melting and its consequences on bacteria-phytoplankton interactions. PIANO will combine experimental studies, carried out in the home lab, and in situ observations during one year at a coastal Antarctic site influenced by ice-sheet melting. The deployment of 2 innovative autonomous samplers (Remote Access Sampler, RAS and Autonomous Clean Environmental sampler, ACE) at Dumont d’Urville will allow a detailed description of the seasonal dynamics of the microbial communities (phytoplankton and bacteria) and their environmental context. The description of the microbial diversity, the identification of the metabolic pathways implicated in the acquisition of glacial Fe and the respective gene transcripts together with the quantification of different chemical forms of Fe will provide original insights to the respective microbial processes and the involved taxa. PIANO will thereby provide a better understanding of a key microbial mechanism likely to influence the Southern Ocean ecological trajectory under climate change conditions.