Life Blooms in Tiny Cities at the Surface of Glaciers

Cryoconite holes (Source:  Joseph Dsilva)
Cryoconite holes (Source: Joseph Dsilva)

You might think glaciers would be hostile to life. But small water-filled holes at the surfaces of glaciers called cryoconite holes contain diverse collections of organisms. Like individual cities in a continent of ice, each hole contains its own distinct population of creatures.

Some scientists believe glaciers should be considered a separate biome given the unique ecosystems that thrive there.

Krzysztof Zawierucha  (Source:  Dwarf)
Krzysztof Zawierucha
(Source: Dwarf)

While the bacteria that live in cryoconite holes have been studied extensively, little is known about the invertebrates that feed on them and on algae found in the holes—only 26 papers have been published on these invertebrates in the past 100 years. Polar biologist Krzysztof Zawierucha from the University of Poznan in Poland and other researchers recently attempted to catalog these invertebrates in a review paper published in the Journal of Zoology.

Cryoconite holes, are created by cryoconite—windblown dust containing rock particles and soot—which darkens the surfaces of glaciers and accelerates melting. Cryoconite holes can form long-lasting habitats given that they are relatively unaffected by rapid environmental changes. These holes can be covered over by ice, or open to the elements.  For a brief explanation of what cryoconite is and how cryoconite holes are created, watch this video:

Only 25 species of cryophilic invertebrates have so far been catalogued and studied, few of them endemic to cryoconite holes. These include insects and two phyla of worms (the ringed worms also known as annelids, and roundworms also known as nematodes), as well as the microscopic rotifers, and the less well known waterbears, whose technical name is  tardigrades.

tardigrades
tardigrades

The species makeup of the cryoconite holes differs slightly in the Arctic, Antarctic, Patagonian, Alpine and Himalayan glaciers where they have been studied. Some of these hole-dwelling invertebrates have geographically restricted ranges, existing only on glaciers in the Alps or Himalayas. The authors suspect there are many more species living in these remote ice holes waiting to be discovered.

The invertebrates are varied in coloration; some are black, others white, and still others are colorless; Zawierucha and his coauthors cite other studies indicating that the coloration may have adaptive value in these environments where ultraviolet radiation is strong. They have different mechanisms for surviving the very low temperatures and the threat of desiccation: some produce very hardy eggs, while others can enter a state of anabiosis—a sort of suspended animation—until conditions improve.

A glacier copepod (scale bar in um), a Plecoptera (scale bar in mm), and tardigrade Pilatobius recamieri (scale bar in um) Source:  Zawierucha et al., 2014.
A glacier copepod (scale bar in um), a Plecoptera (scale bar in mm), and tardigrade Pilatobius recamieri (scale bar in um) Source: Zawierucha et al., 2014.

Cryophilic ecosystems are threatened due to the melting of glaciers caused by climate change and pollution. But cryophilic animals may accelerate the melting of glaciers themselves, particularly those that are black in coloration. Because so little research has been conducted on them, it is possible that some species of cryophilic invertebrate will become extinct before it is catalogued by scientists. If you happen to stumble upon a cryoconite hole on a glacier, treat it with respect. It likely contains an entire world of busy organisms.

For a story on plant spores that live on glacier surfaces, look here.

Satellite Images Offer Clues to Causes of Glacial Lake Flooding

(from journal article: Field observations for glacial lakes: (a) the rapidly expanding Lake Longbasaba in 2012; (b) an areally increasing glacial lake at the Middle Rongbu Glacier near Mount Qomolangma (Everest) in 2008.)
(from journal article: Field observations for glacial lakes: (a) the rapidly expanding Lake Longbasaba in 2012; (b) an areally increasing glacial lake at the Middle Rongbu Glacier near Mount Qomolangma (Everest) in 2008.)

Satellites are now allowing us to track the behavior of icy glacial lakes on the Himalayan Mountains–in particular the conditions that lead to glacial lake outburst floods (GLOFs), which have become increasingly frequent in the region over the past 20 years.

Researchers from the Institute of Mountain Hazards and Environment and the State Key Laboratory of Cryosphere Sciences in China published a study in PLOS One in December of last year that catalogued data from lakes in the central Himalayas between 1990 to 2010.

The scientists, Drs. Yong Nie, Qiao Liu, and Shiyin Liu, used images from Landsat scientific satellites to count and measure glacial lakes in the region. As the longest running remote sensing project, Landsat has over 40 years of images available across the globe.

(from journal article: Distribution of glacial lakes in the central Himalayas)
(from journal article: Distribution of glacial lakes in the central Himalayas)

GLOFs – floods that occur when a lake dammed by a glacier or glacial moraine is released – are hazardous to communities located at elevations below the burst lake. Flooding and debris flows damage infrastructure, cause property loss, and can take lives, as GlacierHub has reported in prior posts. It is widely believed that rising temperatures due to climate change and reduced albedo of the ice from cryoconite (also known as carbon dust particles) are melting the glaciers at higher rates and causing lake volumes to rise, which in turn increases the risk of GLOF events. But the specific processes that lead to GLOF outbursts are not well understood.

By looking at lakes at four time points (1990, 2000, 2005 and 2010), at different elevations (from 3,500 to 6,100 meters), of different types (pro-glacial and supraglacial), and of varying sizes, the researchers were able to identify which lakes expanded faster and burst more frequently to understand which ones pose the greatest risk of GLOFs.

A GLOF from above in Alaska’s Kennai Peninsula (Travis S./Flickr, some rights reserved)
A GLOF from above in Alaska’s Kennai Peninsula (Travis S./Flickr, some rights reserved)

Overall, it was found that total lake surface area for the 1,314 lakes in the central Himalayas had increased over the 20-year period. Drs. Nie, Liu and Liu found that more lakes on the northern side of the central Himalayan range were expanding rapidly. They also found that pro-glacial lakes (lakes at the terminus of a glacier) grew faster than supraglacial lakes (lakes on the surface of the glacier). Some pro-glacial lakes are connected directly to glaciers while others are not, but those that were connected grew far faster. Additionally, larger pro-glacial lakes were likely to flood sooner than smaller ones and more changes to glacial lakes occurred at the altitudes between 4,500 and 5,600 meters.

The dynamics of alpine glacial lakes are complex, but this study could help communities monitor lakes at high risk of flooding and to create early-warning systems and disaster preparedness plans.

PAPER DOI: 10.1371/journal.pone.0083973.g002

GLOF aftermath in Peru ( Will McElwain/Flickr, some rights reserved)
GLOF aftermath in Peru (Will McElwain/Flickr, some rights reserved)