- Hypolith
In
Arctic andAntarctic ecology , a hypolith is aphotosynthetic organism that lives underneath rocks in climatically extremedesert s such asCornwallis Island andDevon Island in theCanadian high Arctic . The community itself is the hypolithon.Hypolithons are protected from harsh
ultraviolet radiation andwind scouring by their rock, which can also trap moisture. The rocks are generallytranslucent to allow for the penetration oflight . Writing in "Nature", ecologistCharles S. Cockell of theBritish Antarctic Survey and Dale Stokes describe how hypoliths reported to date (until 2004) had been found underquartz , which is one of the most common translucent rocks [cite journal
journal=Nature|volume=431|pages=414|date=23 September 2004|doi=10.1038/431414a|title=Widespread colonizationby polar hypoliths|author=Charles S. Cockell|coauthors=M. Dale Stokes] .However, Cockell reported that on Cornwallis Island and Devon Island, 94-95% of a
random sample of 850 opaque dolomitic rocks were colonized by hypoliths, and found that the communities were dominated bycyanobacteria . The rocks chosen were visually indistinguishable from those nearby, and were about 10cm across; the hypolithon was visible as a greenish coloured band. Cockell proposed that rock sorting byperiglacial action, including that during freeze–thaw cycles, improves light penetration around the edges of rocks (seegranular material andBrazil nut effect ).Cockell and Stokes went on to estimate the
productivity of the Arctic communities by monitoring the uptake ofsodium bicarbonate labelled withCarbon-14 and found that (for Devon Island) productivity of the hypolithon was comparable to that ofplant s,lichen s, andbryophyte s combined (0.8 ± 0.3 g m-2 y-1 and 1 ± 0.4 g m-2 y-1 respectively) and concluded that the polar hypolithon may double previous estimates of the productivity of that region of the rocky polar desert. [cite journal
journal=Arctic, Antarctic, and Alpine Research|pages=335–342
title=Hypolithic Colonization of Opaque Rocks in the Arctic and Antarctic Polar Desert
author=Charles S. Cockell
coauthors=M. Dale Stokes
volume=38
issue=3
month=Aug
year=2006|doi=10.1657/1523-0430(2006)38 [335:HCOORI] 2.0.CO;2]See also
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Endolith References
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