ý.,,: V. ý ýý . - Nottingham eTheses - University of Nottingham

1999 ; Hand & Burton, 1981) or identified using molecular techniques (e. g. DGGE.
Murray et al., 1998).
1.4 -
Antarctic oases -
ice-free refugia.
The Antarctic continent is one of the driest and coldest places on Earth. Less than
5% of the continent is free of ice. Seventy-five percent of the world's freshwater is
locked up in its vast ice cap, which in places can reach a thickness of 4km. However.
liquid water is available in its ice-free areas. Some areas have been ice-free for up to five
million years such as the southern Victoria Land desert oasis (Parker et al., 1982); others
such as the Larsemann Hills, Syowa Oasis, Schirmacher Oasis, Bunger Hills and the
Vestfold Hills are all considerably younger (Hand & Burton, 1981; Laybourn-Parry,
1997; Bell & Laybourn-Parry, 1999b) and mostly formed by iso-static uplift caused by
the retreat of the Antarctic ice-cap approximately 9,000 years ago after the Winconsonian
glaciation (Burton, 1981; Franzmann, 1991; Burgess et al., 1994).
This study concentrates on the lakes of the Vestford Hills, Eastern Antarctica
(68°S, 77-78°E, Fig. 2.1a), but also includes some lakes from the Larsemann Hills
(69°23' S, 76°23'E, Fig 2.1 b) and Beaver Lake, an epi-glacial lake in MacRobertson Land
(70° 48'S, 68°15'E, Fig 2.1c). The Vestfold Hills contain around 300 lakes and ponds,
most of which are of marine origin. During isostatic uplift pockets of seawater
in hollows
and fjords were cut off. Those lakes with inflows and outflows were progressively
flushed by glacial and snow meltwaters and evolved into freshwater systems. However,
lakes without outlets (i. e. endorehic basins) evolved into brackish, saline and hypersaline
lakes some of which have undergone meromixis (Laybourn-Parry et al., 2002).
Therefore, the action of evaporation, freezing concentration and marine and melt water
influx have altered the salinity and anion/cation ratio of each of the lakes (James et al.,
1994; Gore et al., 1996a). The lakes vary from freshwater to 350 0o salinity (Pickard,
1986; Laybourn-Parry et al, 2002). Some lakes also show thermal and chemical
stratification, which is either seasonal or meromictic (Burton, 1981; Pickard, 1986).
The microbial diversity of the lakes and soil in the Vestford Hills has been
researched (Wright & Burton, 1981; Burke & Burton, 1988; Franzmann, 1991;
Franzmann & Rohde, 1991; Franzmann & Rohde, 1992; Laybourn-Parry & Marchant,
1992a & 1992b; Laybourn-Parry et al., 1992; Franzmann & Dobson, 1993 ; Perriss et al..
3