Miniature Ecosystems on the Ice
ILULISSAT, GREENLAND– Here’s your bit o’ science jargon for the day: cryoconite. It’s a word I encountered in the Dry Valleys of Antarctica seven years ago and had forgotten about until the other day when I encountered cryoconites of top of the Jacobshavn glacier near Ilulissat.
Essentially they are small round pools of water on the top of a glacier that have a layer of dirt on the bottom. But here’s the amazing thing about cryoconites: they harbor a complete ecosystem with single-celled photosynthetic bacteria and algae that are eaten by tiny nematodes, rotifers, and tardigrades (“water bears”) that are, in turn, eaten by carnivorous tardigrades.
I knew that about Antarctic cryoconites, but I wasn’t sure about the Arctic variety so we searched out a bookstore in Ilulissat today and I looked it up in the “Ecology of Greenland.” Sure enough, this textbook, published in 2001 in English, Danish and Greenlandic, answered my question: the little melt-holes on ice contain six species of tardigrades. The most common, Diphascon recameri, can be found in abundance; one study counted 367 water bears in a 10 ml sample found on the Jakobshavn glacier. Tardigrades have even been found 80 meters below the surface happily making a living in cryoconite dust that washes down deep ice crevices.
The cryoconites themselves start when a bit of wind-blown dust containing these hardy organisms lands on the ice. The dark color of the dust absorbs more of the sun’s energy than white ice and melts a hole in the ice sheet. The holes can reach a depth of 20 cm and we saw hundreds of these little aquaria everywhere we walked on the ice. On a summer day, even though the surrounding ice is below freezing, the temperature of the dust at the bottom of a cryoconite can reach 6 degrees C, a cozy environment for its inhabitants.
Isn’t life amazing that it can even eke it out on top of an ice sheet?