Description: The diatom flora of three lakes in the ice-free Amery Oasis, East Antarctica, was studied. Two of the lakes are meltwater reservoirs, Terrasovoje Lake (31 m depth) and Radok Lake (362 m depth), while Beaver Lake (〉435 m depth) is an epishelf lake. The lakes can be characterized as cold, ultra-oligotrophic and alkaline, displaying moderate (Radok and Terrasovoje lakes) to high (Beaver Lake) conductivities. There was no diatom phytoplankton present in any of the three lakes. While 34 benthic diatom taxa were identified from modern and Holocene sediments of Terrasovoje and Radok lakes, a 30-cm long sediment core recovered in Beaver Lake was barren. Five species (Luticola muticopsis, Muelleria peraustralis, Pinnularia cymatopleura, Psammothidium metakryophilum, P. stauroneioides) are endemic to the Antarctic region. All identified taxa are photographically documented and brief notes on their taxonomy, biogeography and ecology are provided. The most abundant diatom taxa are Amphora veneta, Craticula cf. molesta, Diadesmis spp, M. peraustralis and Stauroneis anceps. This is the first report on the diatom flora in lakes of the Amery Oasis.

Description: The late Quaternary palaeoenvironmental history of the southern Windmill Islands, East Antarctica, has been reconstructed using diatom assemblages from two long, well-dated sediment cores taken in two marine bays. The diatom assemblage of the lowest sediment layers suggests a warm climate with mostly open water conditions during the late Pleistocene. During the following glacial, the Windmill Islands were covered by grounded ice preventing any in situ bioproductivity. Following deglaciation, a sapropel with a well-preserved diatom assemblage was deposited from ~10 500 cal yr BP. Between ~10 500 and ~4000 cal yr BP, total organic carbon (Corg) and total diatom valve concentrations as well as the diatom species composition suggest relatively cool summer temperatures. Hydrological conditions in coastal bays were characterised by combined winter sea-ice and open water conditions. This extensive period of glacial retreat was followed by the Holocene optimum (~4000 to ~1000 cal yr BP), which occurred later in the southern Windmill Islands than in most other Antarctic coastal regions. Diatom assemblages in this period suggest ice-free conditions and meltwater-stratified waters in the marine bays during summer, which is also reflected in high proportions of freshwater diatoms in the sediments. The diatom assemblage in the upper sediments of both cores indicates Neoglacial cooling from ~1000 cal yr BP, which again led to seasonally persistent sea-ice on the bays. The Holocene optimum and cooling trends in the Windmill Islands did not occur contemporaneously with other Antarctic coastal regions, showing that the here presented record reflects partly local environmental conditions rather than global climatic trends.

Description: The late Quaternary palaeoenvironmental history of the southern Windmill Islands, East Antarctica, has been reconstructed using diatom assemblages from two long, well-dated sediment cores taken in two marine bays. The diatom assemblage of the lowest sediment layers suggests a warm climate with mostly open water conditions during the late Pleistocene. During the following glacial, the Windmill Islands were covered by grounded ice preventing any in situ bioproductivity. Following deglaciation, a sapropel with a well-preserved diatom assemblage was deposited from ~10500 cal yr BP. Between ~10500 and ~4000 cal yr BP, total organic carbon (Corg) and total diatom valve concentrations as well as the diatom species composition suggest relatively cool summer temperatures. Hydrological conditions in coastal bays were characterised by combined winter sea-ice and open water conditions. This extensive period of glacial retreat was followed by the Holocene optimum (~4000 to ~1000 cal yr BP), which occurred later in the southern Windmill Islands than in most other Antarctic coastal regions. Diatom assemblages in this period suggest ice-free conditions and meltwater-stratified waters in the marine bays during summer, which is also reflected in high proportions of freshwater diatoms in the sediments. The diatom assemblage in the upper sediments of both cores indicates Neoglacial cooling from ~1000 cal yr BP, which again led to seasonally persistent sea-ice on the bays. The Holocene optimum and cooling trends in the Windmill Islands did not occur contemporaneously with other Antarctic coastal regions, showing that the here presented record reflects partly local environmental conditions rather than global climatic trends.

Description: To establish a natural background and its temporal and spatial variability for the area around Casey Station in the Windmill Islands, East Antarctica, the authors studied major and trace element concentrations and the distribution of organic matter in marine and lacustrine sediments. A wide range of natural variability in trace metal concentrations was identified between sites and within a time scale of 9 ka (e.g., Ni 5-37 mg/kg, Cu 20-190 mg/kg, Zn 50-300 mg/kg, Pb 4.5- 34 mg/kg). TOC concentrations are as high as 3 wt.% at the marine sites and 20 wt.% at the lacustrine sites, and indicate highly productive ecosystems. These data provide a background upon which the extent of human impact can be established, and existing data indicate negligible levels of disturbance. Geochemical and lithological data for a lacustrine sediment core from Beall Lake confirm earlier interpretation of recent climatic changes based on diatom distribution, and the onset of deglaciation in the northern part of the Windmill Islands between 8.6 and 8.0 ka BP. The results demonstrate that geochemical and lithological data can not only be used to define natural background values, but also to assess long-term climatic changes of a specific environment. Other sites, however, preserve a completely different sedimentary record. Therefore, inferred climatic record, and differences between sites, can be ascribed to differences in elevation, distance from the shore, water depth, and local catchment features. The extreme level of spatial variability seems to be a feature of Antarctic coastal areas, and demonstrates that results obtained from a specific site cannot be easily generalized to a larger area.