No evidence of phago-mixotropy in Micromonas polaris , the dominant picophytoplankton species in the Arctic

In the Arctic Ocean, the small green alga dominates pico-phytoplankton during the summer months. It has been previously hypothesized to be phago-mixotrophic (capable of bacteria ingestion) based on laboratory and field experiments. Prey uptake was analysed in several strains isolated from different regions and depths of the Arctic Ocean. Using both fluorescent beads and fluorescently labelled bacteria as prey, we found no evidence of phago-mixotrophy in any strain by flow cytometric measurement of prey ingestion. In addition, predictions reveal that members of the genus lack a genetic signature of phagocytotic capacity.