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Cyanobacteria in Antarctic Lake Environments

2007; Springer Nature (Netherlands); Linguagem: Inglês

10.1007/978-1-4020-6112-7_16

1566-0400

Shiv M. Singh, Josef Elster,

Protist diversity and phylogeny

The Antarctic habitats are some of the driest and coldest ecosystems on the Earth. Earlier there was a general acceptance that polar deserts harbored little life (Priscu, 1999). But, recent studies have revealed the existence of microbes in: the snow near the South Pole (Carpenter et al., 2000), the 3.5 km deep in Vostok ice (Karl et al., 1999; Priscu et al., 1999a), exposed soils (Wall and Virginia, 1998), sandstones (Friedmann et al., 1993), meltwater ponds (Vincent, 1988), liquid water column of permanently ice-covered lakes (Priscu et al., 1999b), and the ice covers of permanent lake ice (Priscu et al., 1998; Psenner et al., 1999). Most of the microbes found in these habitats are prokaryotic (Vincent, 1988; Gordon et al., 2000; Brambilla et al., 2001). Among these microbes, one of the most important components is the photosynthetically active cyanobacteria. They provide for an adequate quantity of fixed carbon via photosynthesis to drive a well-developed ecosystem (Vincent, 1988). On the contrary, in those habitats where there is a lack of cyanobacteria, biomass production by the addition of new carbon and nitrogen is slowed. Thus, such habitats are poor in biodiversity and also poor in trophic levels. In Antarctic habitats the cyanobacteria are adapted and acclimated to their environment in terms of temperature, freeze/thaw survival photoprotection, as well as light acquisition for photosynthesis (Vincent et al., 1993a, b, c; Tang et al., 1997; Nadeau et al., 1999; Tang and Vincent, 1999; Nadeau and Castenholz, 2000). Though cyanobacteria play a significant role in ecosystem dynamics, only a few of them have been considered true psychrophiles (Tang et al., 1997; Fritsen and Priscu, 1998). They are classified as psychrotolerant or psychrotrophic due to their ability to metabolize near 0ºC and also because their temperature optima for growth are typically above 15ºC. Some of the cyanobacterial groups, for example, Leptolyngbya, Phormidium, Oscillatoria, and Nostoc are cosmopolitan and occur in highly divergent environmental extremes.