The effects of Ultraviolet-B radiation on Antarctic sea-ice algae1
Ryan, KG and McMinn, A and Hegseth, EN and Davy, SK, The effects of Ultraviolet-B radiation on Antarctic sea-ice algae1, Journal of Phycology, 48, (1) pp. 74-84. ISSN 0022-3646 (2012) [Refereed Article]
The impacts of ultraviolet-B radiation (UVB) on
polar sea-ice algal communities have not yet been
demonstrated. We assess the impacts of UV on
these communities using both laboratory experiments
on algal isolates and by modification of the
in situ spectral distribution of the under-ice irradiance.
In the latter experiment, filters were attached
to the upper surface of the ice so that the algae
were exposed in situ to treatments of ambient levels
of PAR and UV radiation, ambient radiation minus
UVB, and ambient radiation minus all UV. After
16 d, significant increases in chl a and cell numbers
were recorded for all treatments, but there were no
significant differences among the different treatments.
Bottom-ice algae exposed in vitro were considerably
less tolerant to UVB than those in situ, but
this tolerance improved when algae were retained
within a solid block of ice. In addition, algae
extracted from brine channels in the upper meter
of sea ice and exposed to PAR and UVB in the laboratory
were much more tolerant of high UVB doses
than were any bottom-ice isolates. This finding indicates
that brine algae may be better adapted to high
PAR and UVB than are bottom-ice algae. The data
indicate that the impact of increased levels of UVB
resulting from springtime ozone depletion on Antarctic
bottom-ice communities is likely to be minimal.
These algae are likely protected by strong UVB
attenuation by the overlying ice and snow, by other
inorganic and organic substances in the ice matrix,
and by algal cells closer to the surface.