@article {4716, title = {Photosynthetic adaptation to polar life: Energy balance, photoprotection and genetic redundancy}, journal = {Journal of Plant Physiology}, volume = {268}, year = {2022}, month = {01/2022}, pages = {153557}, abstract = {

The persistent low temperature that characterize polar habitats combined with the requirement for light for all photoautotrophs creates a conundrum. The absorption of too much light at low temperature can cause an energy imbalance that decreases photosynthetic performance that has a negative impact on growth and can affect long-term survival. The goal of this review is to survey the mechanism(s) by which polar photoautotrophs maintain cellular energy balance, that is, photostasis to overcome the potential for cellular energy imbalance in their low temperature environments. Photopsychrophiles are photosynthetic organisms that are obligately adapted to low temperature (0-15 \°C) but usually die at higher temperatures (\≥20 \°C). In contrast, photopsychrotolerant species can usually tolerate and survive a broad range of temperatures (5-40 \°C). First, we summarize the basic concepts of excess excitation energy, energy balance, photoprotection and photostasis and their importance to survival in polar habitats. Second, we compare the photoprotective mechanisms that underlie photostasis and survival in aquatic cyanobacteria and green algae as well as terrestrial Antarctic and Arctic plants. We show that polar photopsychrophilic and photopsychrotolerant organisms attain energy balance at low temperature either through a regulated reduction in the efficiency of light absorption or through enhanced capacity to consume photosynthetic electrons by the induction of O2\ as an alternative electron acceptor. Finally, we compare the published genomes of three photopsychrophilic and one photopsychrotolerant alga with five mesophilic green algae including the model green alga, Chlamydomonas reinhardtii. We relate our genomic analyses to photoprotective mechanisms that contribute to the potential attainment of photostasis. Finally, we discuss how the observed genomic redundancy in photopsychrophilic genomes may confer energy balance, photoprotection and resilience to their harsh polar environment. Primary production in aquatic, Antarctic and Arctic environments is dependent on diverse algal and cyanobacterial communities. Although mosses and lichens dominate the Antarctic terrestrial landscape, only two extant angiosperms exist in the Antarctic. The identification of a single \‘molecular key\’ to unravel adaptation of photopsychrophily and photopsychrotolerance remains elusive. Since these photoautotrophs represent excellent biomarkers to assess the impact of global warming on polar ecosystems, increased study of these polar photoautotrophs remains essential.

}, keywords = {LTER-MCM, genomic redundancy, light, photoprotection, photopsychrophily, photopsychrotolerance, Photosynthesis, temperature}, doi = {10.1016/j.jplph.2021.153557}, url = {https://www.sciencedirect.com/science/article/pii/S0176161721001966}, author = {H{\"u}ner, Norman P. A. and Smith, David R. and Cvetkovska, Marina and Zhang, Xi and Alexander G. Ivanov and Szyszka-Mroz, Beth and Kalra, Isha and Rachael M. Morgan-Kiss} } @article {4613, title = {Year-round and long-term phytoplankton dynamics in Lake Bonney, a permanently ice-covered Antarctic lake}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {126}, year = {2021}, month = {04/2021}, pages = {e2020JG005925}, abstract = {

Lake Bonney (McMurdo Dry Valleys, east Antarctica) represents a year-round refugium for life adapted to permanent extreme conditions. Despite intensive research since the 1960s, due to the logistical constraints posed by 4-months of 24-h darkness, knowledge of how the resident photosynthetic microorganisms respond to the polar winter is limited. In addition, the lake level has risen by more than 3 m since 2004: impacts of rapid lake level rise on phytoplankton community structure is also poorly understood. From 2004 to 2015 an in situ submersible spectrofluorometer (bbe FluoroProbe) was deployed in Lake Bonney during the austral summer to quantify the vertical structure of four functional algal groups (green algae, mixed algae, and cryptophytes, cyanobacteria). During the 2013\–2014 field season the Fluoroprobe was mounted on autonomous cable-crawling profilers deployed in both the east and west lobes of Lake Bonney, obtaining the first daily phytoplankton profiles through the polar night. Our findings showed that phytoplankton communities were differentially impacted by physical and chemical factors over long-term versus seasonal time scales. Following a summer of rapid lake level rise (2010\–2011), an increase in depth integrated chlorophyll a (chl-a) occurred in Lake Bonney caused by stimulation of photoautotrophic green algae. Conversely, peaks in chl-a during the polar night were associated with an increase in mixotrophic haptophytes and cryptophytes. Collectively our data reveal that phytoplankton groups possessing variable trophic abilities are differentially competitive during seasonal and long-term time scales owing to periods of higher nutrients (photoautotrophs) versus light/energy limitation (mixotrophs).

}, keywords = {LTER-MCM, algae, Antarctic, fluorometry, ice, lakes, light, profiling, winter}, issn = {2169-8953}, doi = {10.1029/2020JG005925}, url = {https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JG005925}, author = {Patriarche, Jeffrey D. and John C. Priscu and Cristina D. Takacs-Vesbach and Winslow, Luke A. and Myers, Krista F. and Heather N. Buelow and Rachael M. Morgan-Kiss and Peter T. Doran} }