Antarctic snow algal responses to temperature - potential implications of climate change

Snow algae are important primary producers in Antarctic terrestrial ecosystems. As short-term Antarctic summer temperatures approach 20°C, parameterising temperature tolerance for snow algal species is key to determining how climate change may affect community composition and primary productivity. We studied three Antarctic snow algae strains isolated from Ryder Bay, Adelaide Island (Antarctic Peninsula). The strains were exposed to 4, 8, 10, 12, 16 and 20°C across four laboratory experiments to assess the effects of temperature on growth, metabolite composition and photochemistry. Growth of Limnomonas sp. and Chlorominima sp. was negatively affected at 8°C and they did not survive at 20°C. Micractinium sp. conversely, grew well at all temperatures and displayed metabolic profiles similar to those of the temperate alga, Chlorella vulgaris. Photosynthetic parameters, measured by quantum yield (QY) curves, O2 production and pigment content, were minimally affected by temperature in Micractinium sp., whereas Limnomonas sp. showed reduced QY at temperatures of 8°C and above. Chlorominima sp. exhibited the greatest variation in QY and O2 production across temperature treatments. Our findings suggest that increased temperatures are likely to lead to changes in cryomicrobial community composition, with the psychrotolerant Micractinium sp. being more resilient to these changes.