Photosynthesis and Stress Tolerance in Communities of Antarctic Snow Algae

Abstract

In maritime Antarctic snow algae form ubiquitous and diverse communities, whose dynamics and biogeochemical processes influence atmospheric, terrestrial, freshwater and marine realms. However, these biomes have been little studied in relation to photophysiological features and environmental tolerance despite their high sensitivity to climate change. Photochemical responses of major groups of photoautotrophs inhabiting red, orange and green snow in King George Island (Antarctic) to solar radiation (including UV wavelengths) were simultaneously investigated through multichannel chlorophyll fluorometry, both in laboratory and under natural sunlight. Multivariate analysis indicated siteand type of snow dependent differences in algal groups and photosynthetic characteristics: chlorophyceans dominated in green and red snow from a glacier site, while in green and orange snow of coastal areas or in the vicinity of bird colonies cyanobacteria and chl ccontaining organisms were well represented. Chlorophyta and cyanobacteria from green snow showed highest UV sensitivity of maximum quantum yield (Fv/Fm), while red snow, especially from glacial sites were less sensitive. Exposure for 3 h to natural solar radiation at midday revealed a welldeveloped dynamic photoinhibition (decreases between 80 and 100%) followed by recovery rates up to close 100 %. Temperature affected photosynthetic responses to UV radiation: in general algae from green snow were more sensitive compared to red snow, especially at 20 ºC. In contrast, 2ºC did not exacerbate the UV effects on photosynthesis.