Two Wrongs Make a Right: High Salinity and Low Light Intensity Protects Polar Algae from Heat Stress

• Main Author: Osmers, Pomona
• Other Authors: Cvetkovska, Marina
• Format: Thesis
• Language: English
• Published: Université d'Ottawa / University of Ottawa
• Subjects: climate change; algae; polar; psychrophiles; Arctic; Bonney; Lake Bonney; Antarc*; Antarctica; Climate change
• Online Access: http://hdl.handle.net/10393/45640; https://doi.org/10.20381/ruor-29844

The world is dominated by cold environments that include the poles, the deep ocean, and alpine regions. Polar algae support the aquatic food chain and are increasingly threatened by climate change. With a changing climate, ice cover is decreasing with increased temperatures, leading to changes in light availability and salinity. Using two closely related but geographically distant algal species, Chlamydomonas priscuii and Chlamydomonas malina, we examined how the heat stress responses changed depending on their culturing conditions. C. malina was isolated from the Beauford Sea in the Canadian Arctic and C. priscuii is from the permanently ice-covered Lake Bonney, Antarctica. This work looks at two questions; (1) how cold adapted algae responds to changing conditions and subsequent heat stress, and (2) what contributes to stress resistance? We found that algae show robust growth across a wide spectrum of light and salinity but have the fastest growth rates at low salinity and high light intensities. These fast-growing algae are the most susceptible to heat stress indicating liability during climate change. High salinity grown algae were more resilient when challenged by heat stress in the terms of maintaining photosynthetic efficiency, attenuated ROS production, and delayed cell death. At high salinity C. priscuii produces high levels of glycerol which for the first time in green algae has been shown to contribute to thermotolerance. Overall, this work provides insight into the stress resilience of psychrophiles, something that is especially pertinent in our age of rapid climate change.