| dc.description.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. | |
