In Arctic and Antarctic ecology, a hypolith is a community of photosynthetic organisms, and extremophiles, that live underneath rocks in climatically extreme deserts such as Cornwallis Island and Devon Island in the Canadian high Arctic.
Hypolithons are protected by their rock from harsh ultraviolet irradiation and wind scouring.
Writing in Nature, ecologist Charles S. Cockell of the British Antarctic Survey and Dale Stokes (Scripps Institution of Oceanography) describe how hypoliths reported to date (until 2004) had been found under quartz, which is one of the most common translucent minerals.
The rocks chosen were visually indistinguishable from those nearby, and were about 10 cm across; the hypolithon was visible as a greenish coloured band.
Cockell and Stokes went on to estimate the productivity of the Arctic communities by monitoring the uptake of sodium bicarbonate labelled with Carbon-14 and found that (for Devon Island) productivity of the hypolithon was comparable to that of plants, lichens, and bryophytes 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.