Bunger Hills

Location The Bunger Hills is a rocky, ice-free area located in eastern Antarctica (66° 17' S) and is surrounded on all sides by glacial ice. This region is thus different from Vestfold Hills, which has the open ocean as one of its boundaries, but similar to Schirmacher Hills, which is also surrounded by glaciers. The total area is about 950 km2, of which 420 km2 is exposed rock. Most lake studies have occurred in the southern Bunger Hills, which has a maximum relief of about 160 m and is dissected by many steep valleys filled by lakes. Lakes also occur in the till-covered lowlands, but are generally smaller and more circular in shape. The climate of the Bunger Hills is similar to that of other rocky coastal areas of the East Antarctic coastline and most closely related to that of the Vestfold Hills.

Formation and diversity Over 200 water bodies occur in the Bunger Hills, ranging in size from small, shallow ponds that freeze to the bottom during winter, to Algae Lake, one of the largest and deepest surface freshwater lakes in Antarctica (14.3 km2, 143 m deep). The conductivity of the lakes ranges from ultrafresh (<20mgl~1 total dissolved solids (TDS)) for those which receive melt water from the Antarctic plateau, to highly mineralized (>80 gl-1 TDS).

Russian scientists working on these lakes characterized four types depending upon their hydrological and chemical characteristics (Table 3).

The lakes of the Bunger Hills differ from other coastal Antarctic lakes in the presence of a relatively high number of epishelf lakes. Owing to their position between land and a floating ice shelf or glacier, these lakes are tidal, containing a layer of freshwater overlying the water derived from the adjacent marine environment (Figure 2). The degree to which marine incursion occurs depends upon the actual hydraulic potential of the lake. Higher inflows produce hydrostatic pressure that minimizes the movement of marine water into the lake, whereas lower inflows allow marine water to enter the lake basin. Only about 10 known examples of this type of lake exist and are believed to have provided important refuges for aquatic organisms during glacial periods.

The biology of lakes in the Bunger Hills has received relatively little study to date. Research by Russian and Australian scientists revealed that the larger lakes have low water column primary production (0.08-326 mg carbon per cubic meter per day) and phytoplankton biomass (chlorophyll a is typically <2 mg l_1). The highest production occurs in lakes with the highest salinities. Despite low water column primary productivity, microbial mats exist in nearly all lakes of the Bunger Hills and consist of cyanobacteria, chlorophytes, diatoms, mosses, and heterotrophic grazers.

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