Waimangu Stream

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    Various forms of life have adapted to live in the extreme environment of New Zealand's geothermal aquatic environments. This stream, which averages 45-55°C, flows out of the main crater lake in Waimangu Valley. Small fountains of near boiling water (96-99°C) bubble up along its edge, identifiable by the dark brown patches. Kanuka (the shrub growing in the middle of this stream) and several blechnum ferns, with specially adapted shallow root systems that do not penetrate more than 3-5 cm into the soil (to avoid the near-boiling groundwater), make up the shrubby vegetation. A multitude of microoganisms, both thermophiles and thermotrophs, grow in colorful mats in the shallow stream water. The boundaries between brown and green occur where the water temperature changes from >55-60°C to <55-60°C. Above 60°C, photosynthesis is inhibited; the archea and bactieria that live in this region do not use chlorophyll to genreate energy (instead they rely on the oxidation of other compounds, such as Fe2+). As the water flows over the riverbank surface and cools, photosynthetic cyanobacteria (blue-green algae) are able to grow in dark green mats.
    Waimangu Volcanic Valley is the world's youngest geothermal system. It is believed to have originated in the 1886 Mount Tarawera eruption, which created a 14 km crack in the eath's crust between the mountain and Lake Rotomahana. Waimangu means "black water" in Maori, which proabably comes from the dark thermal pools that are rich in iron sulfides (a product of the thermophiles oxidation reactions).
     
    www.rotorua.nz.com/waimangu.aspx
    www.teara.govt.nz/en/hot-springs-mud-pools-and-geysers/3/5
    www.tandfonline.com/doi/abs/10.1080/00288330.1969.9515311

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