Thriving on Winter Food
Microalgae, like higher plants, are photoautotrophic and use photosynthesis to capture carbon from the air with sunlight. However, many microalgae in the cold Antarctic seas can also live in a more animal-like way by consuming other algae and organic matter in seawater. This mixotrophic lifestyle helps them survive the dark polar winters and springs, giving them a head start in the new season, says Susanne Wilken, an ecological researcher at the Institute for Biodiversity and Ecosystem Dynamics (IBED) at the University of Amsterdam (UvA).
Anti-freeze Results in Cloud Formation
Antarctic microalgae have another unique characteristic: they produce dimethylsulphoniopropionate (DMSP), which acts as a salt regulator and anti-freeze, helping them survive in sea ice. When the ice melts, they release DMSP, which breaks down into dimethyl sulfide (DMS), a gas that promotes cloud formation and blocks sunlight. Thus, by degrading their anti-freeze, microalgae play a crucial role in climate regulation.
Relationship Between Eating Style of Algae and Climate Change
Wilken collaborates with mass spectrometrist Gertjan Kramer from the Swammerdam Institute for Life Sciences (SILS) at UvA and phytoplankton ecophysiologist Jacqueline Stefels from the University of Groningen, funded by the Netherlands Polar Programme (NPP). The team, including researchers from the British Antarctic Survey, explores the relationship between the mixotrophic lifestyle of microalgae and their role in global carbon and sulfur cycles, which is significant for climate change. They hypothesize a strong relationship between mixotrophy and sulfur-containing anti-freeze due to their role in surviving polar ice.
To investigate this, the scientists will conduct research in the Antarctic waters and sea ice over the next five years. Using the Dutch Dirck Gerritsz Laboratory at the British Antarctic Survey's Rothera research station, they will measure the contributions of photosynthesis and organic matter feeding to microalgae growth. Laboratory studies will use proteomics to study protein interactions between mixotrophy and DMS production and examine the role of mixotrophic organisms in biogeochemical cycles and atmospheric DMS concentrations.
Warning Against Climate Effects
Mixotrophic microalgae have an advantage over other algae that cannot grow in sea ice during winter, but this is dependent on sufficient winter sea ice. With Antarctic sea ice reaching record lows last year, the future growth of microalgae could be affected. Wilken warns that the research may reveal how melting sea ice reduces the cooling effect of microalgae on the climate, highlighting the accelerating impacts of climate change.
