Molecular mechanisms of the acclimation and adaptation of the oceanic phytoplankton Pelagomonas calceolata to its environment – PelagoAdapt

Marine phytoplankton account for more than 45% of total net primary production and play an essential role in supplying organic matter to marine food webs. A global decline of phytoplankton biomass has been reported over the past century (1% of chlorophyll-a concentration per year), leading to a decrease of net primary production in many oceanic regions. Temperature-driven reductions in phytoplankton productivity are likely to have cascading effects on higher trophic levels and ecosystem functioning. However, it is extremely challenging to predict the potential capacity of phytoplanktonic organisms to acclimate or adapt to rising temperatures and variations in nutrient availability. In the PelagoAdapt project, we propose to use Pelagomonas calceolata, which is a cosmopolitan and abundant pico-phytoplanktontic, as a model organism to study molecular mechanisms of acclimation and adaptation of open-ocean phytoplankton to climate change. In light of the ecological success of P. calceolata in oceanic environments, we hypothesize that this organism: 1) has developed specific molecular mechanisms to rapidly modulate gene expression in response to physico-chemical variations 2) is a fast-evolving species with many variants in key genes facilitating adaptation 3) and therefore will proliferate in the future at the expense of phytoplanktonic organisms more affected by global warming. The overarching objectives of the PelagoAdapt project are to identify the genes involved in responses of an open ocean photosynthetic picoeukaryote (PPE) to warming and associated environmental change and to characterize the regulation of these genes over ecological to evolutionary time-scales using environmental samples from the Tara expeditions as well as laboratory culture experiments.