Life in a cold environment - Antarctica: Global Science from a Frozen Continent - page 200

Figure 6.24 Cryptoendolithic community living within Beacon sandstone in the Dry Valleys.

The green layer towards the top is of algae and cyanobacteria, the white layer in the centre
is fungus and the black layer at the bottom is the two combined as a lichen. These communities
may grow for only a few hours each year when there is liquid water and warmer temperatures
and thus may be many thousands of years old (Credit: Chris Gilbert, BAS).

Freshwaters

Freshwaters are poorly represented in the Antarctic relative to other continents.
There are few true rivers, and these are short - the longest being the few kilometres

of the Onyx River in the Dry Valleys although there are many ephemeral melt

streams during the short Antarctic summer. Freshwater lakes have been subject to
detailed study on some sub-Antarctic islands, in parts of the maritime Antarctic
(South Orkney and South Shetland Islands), along the continental coastline
(Larsemann and Davis areas, Syowa) and in Victoria Land. The latter region
includes some particularly unusual lakes within the Dry Valleys, ranging from
freshwater to hypersaline. As with terrestrial ecosystems, those of freshwaters have a
very simple structure. There is again an absence of vertebrates (

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(fish, amphibians).

Higher trophic levels are again very limited for instance there is only a single

predatory diving beetle, and that is limited to sub-Antarctic South Georgia, a
single predatory copepod in the maritime Antarctic, and no predatory Crustacea
in the whole of the continental Antarctic. Microbial foodwebs assume an importance

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