Antarctic Lakes as Models for the Study of Microbial Biodiversity, Biogeography and Evolution

The Antarctic continent is almost entirely covered by a vast icecap that reaches 4 km in thickness. Despite this, the continent possesses a remarkable array of lake ecosystems, many of them located in the small ice-free coastal areas or Antarctic oases, so-called because in this continental polar desert they are areas supporting life, albeit sparse. There are some inland ice-free areas that also have lake ecosystems, notably the largest icefree expanse of the Dry Valleys in Southern Victoria Land (Figure 3.1). The lakes of these ice-free regions range from freshwater to hypersaline (almost seven times seawater). Some abut onto glaciers, for example, Chelnock Lake (Vestfold Hills) and maintain thick icecovers that may be up to 3–5min thickness (Laybourn- Parry, 2000, unpublished data), while neighbouring lakes may lose their ice for a few weeks in summer, for example, Crooked Lake and Lake Druzhby (Laybourn- Parry et al., 1992; Bayliss et al., 1997). The lakes of the Dry Valleys lie far south (77S) and are among the most extreme Antarctic lacustrine ecosystems. They are covered by debris containing thick ice (up to 4.3 m; Howard-Williams et al., 1998; Spigel & Priscu, 1998). Temporary lakes also often form on glacier surfaces. Although they have not been investigated from a biological perspective, it is probable that their communities closely resemble those of cryoconite holes which are a common feature of glacier surfaces in summer. Such communities are ephemeral.

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