Gigantic ice deserts full of black algae are making the ice melt faster

“A small puddle of melt-water on a glacier can easily have 4,000 different species living in it. They live on bacteria, algae, viruses and microscopic fungi. It’s a whole ecosystem that we never knew existed until recently," said Professor Alexandre Anesio, lead author of the study.

Black algae

The vast sheet of ice the team was investigating was covered by black algae formation, which fascinated the team. “When the ice darkens, it becomes more difficult to reflect sunlight. Instead, heat from the sun's rays is absorbed by the ice, which starts to melt. The more the ice melts, the warmer the temperature on Earth. The algae therefore play an important role in global warming," added Anesio in the press release.

The team assessed that the algae are exponentially making the ice melt faster, approximately by 20%, according to their own estimates. And with global warming, additionally, the springtime melting of snow and ice will occur earlier, which means that the black algae will have more time to grow and spread.

"The algae spread a little more every year. When I travel to Greenland, I now see vast areas where the ice is completely dark because of the algae,” said Anesio.

The team is now looking into the effects of black algae and finding if the growth rate of algae can be slowed down in some way or another. 

Interesting Engineering had earlier reported on how these microorganisms are also found at high elevations, like Mount Everest, which is now acting as a deep freezer for these organisms.

The study was published in the journal Geobiology.

Study abstract:

Glacier and ice sheet surfaces host diverse communities of microorganisms whose activity (or inactivity) influences biogeochemical cycles and ice melting. Supraglacial microbes endure various environmental extremes including resource scarcity, frequent temperature fluctuations above and below the freezing point of water, and high UV irradiance during summer followed by months of total darkness during winter. One strategy that enables microbial life to persist through environmental extremes is dormancy, which despite being prevalent among microbial communities in natural settings, has not been directly measured and quantified in glacier surface ecosystems. Here, we use a combination of metabarcoding and metatranscriptomic analyses, as well as cell-specific activity (BONCAT) incubations to assess the diversity and activity of microbial communities from glacial surfaces in Iceland and Greenland. We also present a new ecological model for glacier microorganisms and simulate physiological state-changes in the glacial microbial community under idealized (i) freezing, (ii) thawing, and (iii) freeze–thaw conditions. We show that a high proportion (>50%) of bacterial cells are translationally active in-situ on snow and ice surfaces, with Actinomycetota, Pseudomonadota, and Planctomycetota dominating the total and active community compositions, and that glacier microorganisms, even when frozen, could resume translational activity within 24 h after thawing. Our data suggest that glacial microorganisms respond rapidly to dynamic and changing conditions typical of their natural environment. We deduce that the biology and biogeochemistry of glacier surfaces are shaped by processes occurring over short (i.e., daily) timescales, and thus are susceptible to change following the expected alterations to the melt-regime of glaciers driven by climate change. A better understanding of the activity of microorganisms on glacier surfaces is critical in addressing the growing concern of climate change in Polar regions, as well as for their use as analogues to life in potentially habitable icy worlds.