|Title||Impact of simulated polar night on Antarctic mixotrophic and strict photoautotrophic phytoplankton|
|Year of Publication||2019|
|Authors||Cariani, ZE, Morgan-Kiss, RM|
|Academic Department||Department of Microbiology|
|Keywords||algae, Antarctic phytoplankton, chlorophyll fluorescence analysis, McMurdo Dry Valleys, Photosynthesis, phytoplankton, polar microbiology, polar night|
Phytoplankton in polar regions experience long periods of continuous darkness annually during the polar night. Due to difficulties in performing field work during this period, it is largely unknown how phytoplankton endure this extreme transition from 24-hour daylight in the fall to several months of total darkness in the austral winter. The primary goal of this study was to compare physiological and photosynthetic responses of several Antarctic phytoplankton of variable trophic abilities (pure photosynthetic vs. mixotrophic) to simulated polar night conditions, including the transition seasons before and after winter. Two distinct responses were observed to extended darkness: (1) strict photoautotrophs (Chlamydomonas sp. ICE-MDV and Chlamydomonas sp. UWO241) exhibited functional downregulation their photosynthetic processes in the winter, followed by a lag phase of several days during mimicked spring, and (2) mixotrophs (Isochrysis sp. MDV and Geminigera cryophila) maintained functional photosynthetic apparatus, increased heterotrophy through the winter, and exhibited immediate growth upon return to light incubation. These differing responses to mimicked polar night conditions could represent two different strategies for surviving the long period of darkness in the phytoplankton’s natural environment.