Phytoplankton Ability to Physiological Acclimatization and Genetic Adaptation to Global Warming

Global warming represents a challenge to the survival of phytoplankton organisms, which are the basis of the aquatic food web and drive essential biogeochemical cycles. We propose a direct experimental research mimicking temperature-increasing scenarios as a novel way to explore the adaptation of phytoplankton to predicted future thermal scenarios. This vulnerability analysis of individual phytoplankton species to increased temperature is key to understand the impact of global warming on aquatic ecosystems. Considering the polyphyletic complexity of the phytoplankton community, we compare the adaptation ability of diverse phytoplankton species from oceanic, coastal and inland waters to global warming, evaluating the role played by physiological acclimatization and genetic adaptation. We found that physiological acclimatization allows survival under the lowest temperature increase. Afterwards pre-existing genetic variability allow some genotypes to survive. Finally, when the temperature rises to a certain threshold, only the occurrence of new mutations that confer thermal resistance assures adaptation. Our results also reveal diverse degrees of tolerance to temperature increase among the different functional groups of phytoplankton, with great inter-specific capacity for genetic adaptation.