Environmental Engineering Reference
In-Depth Information
1. INTRODUCTION
Post-glacial Ace Lake (Fig. 1) is a permanently stratified (meromictic) saline
lake with anoxic, sulfidic, sulfate-depleted and methane-saturated bottom wa-
ters [38]. The sulfidic chemocline at a depth of 12 m is colonized by oblig-
ate anoxygenic photolithotrophic green sulfur bacteria (GSB) of the family
Chlorobiaceae [7], which play a major role in the cycling of carbon and sulfur.
Therefore, Ace Lake may serve as a model system to study large stratified and
anoxic systems such as the Black Sea. Ace Lake was originally a melt-water
filled freshwater lake that became saline due to connection to the sea result-
ing from the Holocene deglaciation and sea-level rise. Isostatic rebound of the
Antarctic continent caused the lake to become re-isolated from the ocean [53].
We expected that these climate-induced variations in the chemical and physi-
cal characteristics of the water column would have had a great impact on the
diversity and abundance of species which thrived in the ancient water column
of Ace Lake.
Figure 1.
(a) The bathymetry of Ace Lake and location of sampling site (depocentre) and (b)
the topographical setting of Ace Lake in the Vestfold Hills, eastern Antarctica (modified after
Swadling [51]).
Preserved organic components provide an archive of ancient aquatic micro-
bial communities and, hence, can be used to reconstruct variations in climate
and its impacts on biodiversity. However, the interpretation of these data is com-
plicated by the often limited specificity of traditional biomarkers, such as lipids
and pigments. The ultimate biomarkers are ribosomal RNA genes (rDNA), the
sequences of which can provide information on the species present by phy-
logenetic comparison. However, in order to identify microorganisms which
