Introduction
The polar regions, both Arctic and Antarctic, show strong evidence of climate change affecting freshwater species, communities, and ecosystems, and are expected to undergo rapid and continued change in the future (IPCC, 2007). Diatoms in the freshwater and brackish habitats of inland waters of the Antarctic provide valuable records of their historic and modern environmental status. Antarctic habitats also contain a unique biodiversity of species many of which are found nowhere else on Earth. In this chapter, we review investigations using diatoms as indicators of environmental change in Antarctic and subantarctic island habitats, including lakes and ponds, streams and seepage areas, mosses and soils, cryoconite holes, brine lakes, and remarkable subsurface glacial lakes.
The Antarctic continent holds the vast majority of the Earth's freshwater, but the water is largely inaccessible because it is in the form of ice. Life is dependent upon liquid water, a substance scarce in Antarctica. Less than 0.4% of the continent is ice free, and it is within these ice-free regions that freshwater lakes and ephemeral streams form, fed by the melting of snow and glacial ice and occasional precipitation. These ice-free regions are located primarily near the Antarctic coastline (Figure 14.1). Of these regions, the “desert oases” of East Antarctica are considered to be the coldest, driest regions on Earth. In the limited parts of these oases where liquid water is available, even if present for only a few short weeks of the year, there is life (McKnight et al., 1999).