Roundup: Contaminated Arctic Spiders, Sand Abundance in Greenland, and Cryoconite on the Tibetan Plateau

Wolf spiders in West Greenland are indicators of metal pollution in mine sites

From Ecological Indicators: “In the Arctic, spiders are the most abundant group of terrestrial predators, with documented abilities to accumulate metals. In Greenland however, most contamination studies in relation to mining have targeted the marine environment, with less attention given to the terrestrial.”

“The contamination status of a terrestrial area can be estimated based on soil sampling and measurements. However, such measurements may be biased due to difficulties in collecting representative soil samples (i.e. caused by high within-site variation of soil contaminants or a lack of information on potential bioavailability of the contaminants investigated). It has therefore been hypothesized that ground dwelling wolf spiders, based on their frequent hunting activities and their active movement over their hunting habitat, would display contamination levels more representative of that area than a specific soil sample.”

Read more about the study here.

Wolf spider in the tundra (Source: Fiona Paton/Flickr)

Greenland’s melting ice sheet releases vast quantities of sand

From Henry Fountain and Ben C. Solomon of the New York Times: “The world makes a lot of concrete, more than 10 billion tons a year, and is poised to make much more for a population that is forecast to grow by more than 25 percent by 2050. That makes sand, which is about 40 percent of concrete by weight, one of the most-used commodities in the world, and one that is becoming harder to come by in some regions.”

“But because of the erosive power of ice, there is a lot of sand in Greenland. And with climate change accelerating the melting of Greenland’s mile-thick ice sheet — a recent study found that melting has increased sixfold since the 1980s — there is going to be a lot more.”

Read the full story here.

Cryoconite on the northeastern Tibetan Plateau enhances melting

From Journal of Glaciology: “Cryoconite is a dark-coloured granular sediment found in supraglacial environments, and it represents an aggregate of mineral particles, black carbon (BC) and organic matter (OM) formed by microbial communities.”

“Compared with snow and ice surfaces, cryoconite typically exhibits stronger light absorption, and its broadband albedo is <0.1 due to its effective absorption of visible and near-IR wavelengths. Thus, cryoconite can effectively influence the mass balance of glacier surfaces.”

Read more about the research here.

Debris and cryoconite at A8 glacier study site (Source: Li et al. 2019)
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Roundup: A Melting Iceberg, Cryoconites, and Lichens

Drifting Icebergs, Bacterial Activity and Aquatic Ecosystems

From BioOne Complete: “The number of icebergs produced from ice-shelf disintegration has increased over the past decade in Antarctica. These drifting icebergs mix the water column, influence stratification and nutrient condition, and can affect local productivity and food web composition. Data on whether icebergs affect bacterioplankton function and composition are scarce, however. We assessed the influence of iceberg drift on bacterial community composition and on their ability to exploit carbon substrates during summer in the coastal Southern Ocean. An elevated bacterial production and a different community composition were observed in iceberg-influenced waters relative to the undisturbed water column nearby.”

Read the research paper here.

Antarctic Peninsula
Antarctic Peninsula (Source: GRID Arendal/Flickr).

The Tibetan Plateau and Cryoconite Bacterial Communities

From Oxford Academic: “Cryoconite holes, water-filled pockets containing biological and mineralogical deposits that form on glacier surfaces, play important roles in glacier mass balance, glacial geochemistry and carbon cycling. The presence of cryoconite material decreases surface albedo and accelerates glacier mass loss, a problem of particular importance in the rapidly melting Tibetan Plateau.”

Learn more about the research here.

Cryoconites (Source: Joseph Dsilva/Flickr).

Lichen Diversity on Glacier Moraines in Svalbard

From BioOne Complete: “This paper contributes to studies on the lichen biota of Arctic glacier forelands. The research was carried out in the moraines of three different glaciers in Svalbard: Longyearbreen, Irenebreen and Rieperbreen. In total, 132 lichen taxa and three lichenicolous lichens were recorded. Eight species were recorded for the first time in the Svalbard archipelago: Arthonia gelidae, Buellia elegans, Caloplaca lactea, Cryptodiscus pallidus, Fuscidea kochiana, Merismatium deminutum, Physconia distorta, and Polyblastia schaereriana. One species, Staurothele arctica, was observed for the first time in Spitsbergen (previously recorded only on Hopen island).”

Read the research paper here.

Lichen in Svalberg (Source: Tim Ellis/Flickr).

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Life, Death and Predation on the Greenland Ice Sheet

The Greenland Ice Sheet is the world’s second-largest body of ice (Source: Krzysztof Zawierucha).
Mention the Greenland Ice Sheet, and chances are that you conjure up the image of a barren, white wilderness, dominated by ice and devoid of life. In fact, the ice sheet and its coastal outlet glaciers support thousands of small pools that teem with bacteria and animals. “A world of microbes exists in these tiny, frozen, cold pools on glaciers. There’s life, death, and predation happening,” marveled glaciologist Aurora Roth.

These little pools are called cryoconite holes, pockets in the surface of glaciers that are usually ovular or circular. Cryoconite holes can be quite small and shallow, or as wide as a meter and up to half as deep. “People first notice cryoconites because they look so odd, like honeycomb. The textures are visually striking,” says Roth. She added that they constitute such an extreme environment that scientists look to them to understand the evolution of simple life forms on Mars and other planetary bodies. A recent paper in Limnology by Krzysztof Zawierucha et al. analyzed cryoconite communities on the margin of the Greenland Ice Sheet and found that the distribution of microfauna at the edge of the sheet is random, without clear ecological determinants like water chemistry or nutrient availability.

Sediment lies at the bottom of cryoconite holes of various sizes (Source: Krzysztof Zawierucha).
Cryoconite holes (and their larger versions, puddles and lakes) are full of water, and contain debris deposited by wind, rockfall or water flow. Small debris particles can be bound together by cyanobacteria into granules, which eventually erode into mud. Both granules and mud foster communities of bacteria and animals that comprise the biotic hotspots of the ice sheet. Microorganisms are the top consumers in cryoconite food chains, a position impossible for them to occupy in most other ecosystems, where they are eaten by larger organisms. Such unusual dynamics make “this icy world more and more fascinating,” Zawierucha told GlacierHub. “Despite the fact that they are in microscopic size, they are apex consumers on the glacier surface, so they are like polar bears in the Arctic or wolves in forests,” he said.

Zawierucha conducted his fieldwork at the beginning of polar autumn and was struck by the changing colors of the tundra, the musk oxen and the impressiveness of the ice sheet, which together created a landscape that felt right out of a fairy tale. As he trekked through wind and rain to collect samples from cryoconite holes, puddles and lakes, he often felt as if he was in a science fiction movie about “icy worlds in other galaxies.”

Zawierucha poses against the dramatic landscape of the ice sheet during fieldwork (Source: Krzysztof Zawierucha).
Back in the lab, Zawierucha found rotifers and tardigrades swimming around in his samples, two hardy invertebrate groups that also live in freshwater, mosses, and for the tardigrade, extreme environments–tardigrades are the only animals that can survive outer space. The invertebrates were far more common in granules than mud. The paper suggests two reasons for this disparity: the mechanical flushing action of water that forms the mud and the food source the granules provide for the invertebrates. The samples boomed with other types of life, as well: they contained thirteen types of algae and cyanobacteria, plus different groups of heterotrophic bacteria.

The flushing process, and the way it affects the animals which it displaces, raises many questions for Zawierucha. How much wind or rain is required to remove the animals from the cryoconites? “How many of them are flushed to downstream ecosystems, and how many stay in the weathering crust on glaciers?” he wonders. And what happens once the animals are out of their holes? Zawierucha harbors what he calls a “small dream,” to find active animals in the subglacial zone (the hydraulic systems under a glacier). “If they are flushed to the icy wells, are they able to survive under ice?” he asks.

Tardigrades are found on all seven continents, in a range of extreme environments (Source: E. Schokraie et al./Wikimedia).
In the future, Zawierucha would like to continue to close what he calls the “huge knowledge gap” between the vast amount of research devoted to microbial ecology on glaciers and the dearth of information about animals. “Even if their distribution is random, they still may play an important ecological role in grazing on other organisms,” he believes.

Tardigrades, some species of which are black in color, may have an even bigger effect on glacial dynamics and global climate. Tiny though they are, populations of black tardigrades in cryoconite holes, which Zawierucha has found on alpine glaciers, can reduce albedo and increase melting of the glacier surface. This may constitute a positive feedback loop that hastens glacial melting, but more studies are required to prove this, Zawierucha says.

One positive feedback loop is clear. Higher temperatures increase the melting of glacier surfaces and spur microbial activity, which in turn speeds up the process of melting, according to Zawierucha. As the Greenland Ice Sheet continues to melt, the animals that call it home will be disturbed, though it is difficult to anticipate the end result. How tardigrades, especially species unique to glacial habitats, will respond to higher flushing rates and removal from glaciers is of particular interest. Perhaps the tardigrades will adapt, or perhaps they will go extinct, says Zawierucha.

Zawierucha prepares samples for transport off the ice sheet (Source: Krzysztof Zawierucha).
Faced with an uncertain future, glaciology projects that cross disciplines make Roth hopeful. “It’s a good example of what happens when you look at a system through an interdisciplinary lens,” she told GlacierHub. “When you bring in a biologist, you see the difference in the questions they ask and things they unearth.”

Now is the time for such interdisciplinary research: more studies of animals living on the Greenland Ice Sheet will help scientists understand how this important freshwater reservoir, and Earth’s climate, will respond to global warming.

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Could Cryoconites Hold the Secrets to Extraterrestrial Life?

In recent years, scientists have found other locations on planets, moons and exoplanets where life might exist. Different animals and organisms like tardigrades (eight-legged microscopic animals commonly known as water bears) have also been sent into space to explore the conditions for survival away from Earth. However, a recent paper published in the journal Contemporary Trends in Geoscience argues that we can look closer to home to understand survival strategies of extraterrestrial life.

More concretely, the authors propose we look to glacier cryoconites, which are granular or spherical mineral particles aggregated with microorganisms like cyanobacteria, algae, fungi, tardigrades and rotifera (another type of multicellular, microscopic animal). Glaciers are among the most extreme environments on Earth due to the high levels of ultraviolet (UV) radiation received and the permanently cold conditions. These factors make them analogous to icy planets or moons.

(Clockwise from top left) An ice sheet in Greenland, cryoconite holes, cryoconite granules, and cryconite granules in high resolution (Source: Zawierucha et al., 2017).

The associations of cryoconites and microorganisms on glaciers are held together in biofilms by extracellular polymeric substances (natural polymers of high molecular weight) secreted by cyanobacteria. They exist as sediment or in cryoconite holes (water-filled reservoirs with cryoconite sediment on the floor) on glacier surfaces.

Cryoconites have been found on every glacier where researchers have looked for them. Cryoconite holes form due to the darkening of color (also termed a decrease in the albedo, or reflectivity of solar radiation) of cryoconite-covered surfaces. The darker color leads to greater absorption of radiation, with an associated warming and increasing melt rates.

“Today we think that simple life forms might have survived on Mars in glacial refugia or under the surface. They can and could have evolved on Saturn and Jupiter’s icy moons,” Krzysztof Zawierucha, the lead author from Adam Mickiewicz University in Poland, shared with GlacierHub. “Imagine a multicellular organism, even a microscopic one, which is able to live and reproduce on an icy moon… It is a biotechnological volcano.”

Earth’s glaciers could be analogous to environments like floating ice on Europa, one of Jupiter’s moons (Source: NASA).

Organisms that live in glaciated regions are adapted to survive in extreme conditions and could provide insights into the survival strategies of extraterrestrial life. Some possess lipids (organic compounds that are not water-soluble), and produce proteins and extracellular polymeric substances that protect them from freezing and drying. Others are able to enter cryptobiotic states in which metabolic activity is reduced to an undetectable level, allowing them to survive extremely harsh conditions.

The microorganisms in cryoconites cooperate and compete, affecting each other’s survival responses. Therefore, previous astrobiological studies, which have only been conducted on single strains of microorganisms, may not reflect the true survival mechanisms of these microorganisms.

Tardigrades can undergo cryptobiosis and survive in the vacuum of space (Source: UNC Chapel Hill/Creative Commons).

In addition, previous astrobiological studies involving some of these microorganisms used terrestrial or limno-terrestrial (moist terrestrial environments that go through periods of immersion and desiccation) taxa, such as moss cushions, which are less likely to be well-adapted to icy planets than their glacier-dwelling cousins.

Tardigrades found in cryoconite have black pigmentation, which probably protects them from high UV radiation. Along with tardigrades, glacier-dwelling rotifera, specifically Bdelloidea, also possess a great ability to repair DNA damage, which confers high resistance to UV radiation. Both may also be better adapted to surviving in constantly near-freezing conditions than terrestrial forms.

“So far, a number of processes analogous to those on Mars and other planets or moons have been found in the McMurdo Dry Valley as well as other dry valleys or brines in sea ice, both of which were considered to be extraterrestrial ecosystem analoguos. There is a great body of evidence that some bacteria and microscopic animals like tardigrades may survive under Martian conditions,” Zawierucha explained.

“Of course, to survive does not mean to be active and to reproduce. Undoubtedly, however, it triggers consideration regarding life beyond Earth, especially in close proximity or connection with permafrost or ice,” he added.

As such, further research about cryoconites could provide insight to mechanisms that enable organisms to survive such extreme conditions. At the same time, cryoconites could also be used in future astrobiological studies to understand how life on other planets functions.

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Small Particles Have Big Impact on Glacial Health

A recent study by Heidi Smith et al. in the desolate McMurdo Dry Valleys of Antarctica has shown that microbial life in biofilms is present across a large part of the region’s ice, suggesting that the stability of polar ice can be influenced by even the smallest of organisms.

Biofilms—thin, slimy bacterial layers that can adhere to a surface—were discovered in conjunction with the windblown dust that accumulates on snow and ice called cryoconite. The research found that a combination of biofilms and cryoconite is capable of enhancing the rate of glacial melting, meaning that the planet may be more vulnerable to sea level rise than previously imagined.

As an important component in the planet’s hydrological and carbon cycles, glacial melting affects sea levels and the chemistry of our oceans. This meltwater enhances the movement of fluids from terrestrial environments to oceans, as well as the transport of nutrients to aquatic ecosystems. In the McMurdo Dry Valleys, the activity of microorganisms on the glacier surface enables the accumulation of organic matter on minerals found in the ice’s dusty cryoconite layers. This relationship results in the darkening of ice over time, making it less efficient at reflecting incoming sunlight than it would be normally. As most of Antarctica’s ice lies atop the continental landmass,  increased melting at the Earth’s southern pole may lead to an appreciable rise in global sea levels.

A view of the Canada Glacier involved in the field study. (Source:Joe Mastroianni, National Science Foundation)
A view of the Canada Glacier involved in the field study (Source: Joe Mastroianni/National Science Foundation).

Prior research in alpine glacial environments and on the Greenland Ice Sheet (Langford et al. 2010) established a correlation between biofilm development and the darkening of cryoconite particles, pointing towards the synergistic possibility of biologically enhanced rates of melting. Until the recent publication of key research by Heidi Smith et al., the role of biofilms in Antarctica was largely unknown.

In conversation with GlacierHub, Smith stated that “the role of biofilms in different glacial locations has not been explored.” She added “due to differences in environmental pressures (temperature extremes, nutrient availability, levels of UV radiation, and rates of flushing), it is possible that the role of biofilms in glacial surface processes varies by location.” Smith’s team was able to establish the precedence of biofilms at extreme southern latitudes in their research and also contributed to the larger body of scientific evidence supporting the role of microbes in influencing reflectivity, otherwise known as albedo, of glaciers.

Smith and her research colleagues employed a variety of methods to investigate the interactions between the biological and mineralogical components of Antarctic ice. Microbial species were identified in the lab via pyrosequencing (which determines the order of nucleotides in DNA by detecting the release of the pyrophosphate ion) as well as epifluorescent microscopy (which utilizes a compound microscope equipped with a high-intensity light source). The team’s research yielded four unique bacterial components in biofilms found in cryoconite holes. Interestingly, Smith told GlacierHub that “while some organisms identified in this study have also been found in cryoconite holes from the Greenland Ice sheet, the relative abundance of individual organisms in each of these locations appears to be geographically distinct.”

The Trans-Antarctic Mountains, a prominent feature in Northern Victoria Land (Source: Hannes Grobe/Alfred Wegener Institute).

The primary region for fieldwork and sampling for the study was an ice-lidded cryoconite hole on the Canada Glacier, located near Victoria Land, Antarctica. When asked about why the team chose to work in this isolated region, Smith replied: “There are previous studies from this region that have focused on cryoconite hole geochemistry, rates of microbial activity and microbial assemblage composition; therefore, we could place samples from this study into a larger framework.”

Following fieldwork on the glacier, subsequent laboratory analysis showed that enriched levels of nitrogen and carbon isotopes were present when Bacteroidetes (one of the four main bacterial phyla) was incubated in the presence of compounds such as sodium bicarbonate and ammonia. These findings point to the conclusion that the spatial organization within a microbially rich biofilm can promote the transfer of chemical compounds and nutrients. Such a result serves to validate the hypothesis that the formation of biofilms may enhance the accumulation of organic material on cryoconite minerals, thus affecting the color and reflectivity of glacial surfaces.

The study concluded that not only are biofilms present in nearly thirty-five percent of cryoconite holes in Antarctica, but that due to regional differences in the distribution of black carbon between the study region and the Arctic, biofilm may play a heightened role (relative to the northern hemisphere) in promoting biological activity on glaciers. Smith added, “In addition to influencing levels of glacial melt, biofilms have the potential to alter marine ecosystems through glacial runoff.” Additionally, she said, “There is also the potential for increases in CO2 release, which contributes to the rising temperatures globally.”

The research by Smith and her team points to important feedback loops with future increases in temperature, as longer melt seasons will stimulate biofilm communities, which alone have the capacity to increase rates of glacial melt. If temperatures continue to rise, the positive feedback between a warmer climate and lower reflectivity on ice surfaces may lead to exponentially faster rates of glacial melt and sea level rise. Overall, these findings illustrate the environment’s sensitivity to the emissions that human populations generate, suggesting that given enough pressure, Antarctic ice may enter a runaway downward spiral of rapid melting. 

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Glaciers Serve as Radioactive Storage, Study Finds

Two cryoconites. Photo courtesy of head researcher Edyta Łokas.
Two cryoconites. Photo courtesy of head researcher Edyta Łokas.

The icy surfaces of glaciers are punctured with cryoconites – small, cylindrical holes filled with meltwater, with thin films of mineral and organic dust, microorganisms, and other particles at the bottom of the hole.

New research conducted by Polish scientists reveals that cryoconites also contain a thin film of extremely radioactive material.

The study confirms previous findings of high levels of radioactivity in the Arctic and warns that as Arctic glaciers rapidly melt, the radioactivity stored in them will be released into downstream water sources and ecosystems.

The study, headed by Edyta Łokas of the Institute of Nuclear Physics at the Polish Academy of Sciences and researchers from three other Polish universities, was published in Science Direct in June.

Sampling during fieldwork. Photo courtesy of Edyta Łokas.

The study examines Hans Glacier in Spitsbergen, the largest and only permanently populated island of the glacier-covered Svalbard archipelago, off the northern Norwegian coast in the Arctic Ocean. While investigating the radionuclide and heavy metal contents of glacial cryoconites, the researchers revealed that the dust retains heavy amounts of airborne radioactive material and heavy metals on glacial surfaces.

This radioactive material comes from both natural and anthropogenic, or human-caused, sources, according to the study. However, the researchers determined through isotope testing that this deposition was mainly linked to human activity.

Head researcher Edyta Lokas says she believes that this radioactive material mainly derives from nuclear weapons usage and testing.

A team researcher in the Hornsund region.
Edyta Lokas in the Hornsund region.

“The radionuclide ratio signatures point to the global fallout [from nuclear weapon testing], as the main source of radioactive contamination on Svalbard. However, some regional contribution, probably from the Soviet tests performed on Novaya Zemlya was also found,” Lokas wrote in an email to GlacierHub.

The Arctic region bears an unfortunate history of radioactive contamination, from an atom bomb going missing at the U.S. base in Thule, Greenland, to radiation from Chernobyl getting picked up by lichens in Scandinavia, making reindeer milk dangerous.

But how does all this radioactive materials end up in the Arctic?

The Arctic, and polar regions in general, often become contaminated through long-range global transport.

In this process, airborne radioactive particles travel through the atmosphere before eventually settling down on a ground surface. While these particles can accumulate in very small, non harmful amounts in soils, vegetation, and animals in all areas of the world, geochemical and atmospheric processes carry the majority of radioactive particles to the Poles.

Once the particles reach the Poles, “sticky” organic substances excreted by microorganisms living in cryoconites attract and accumulate high levels of radioactivity and other toxic metals.

As cryoconites occupy small, but deep holes, on glacier surfaces, they are often left untouched for decades, Edyta explains. Cryoconites also accumulate radioactive substances that are transported with meltwater flowing down the glacier during  summertime.

Hans Glacier in Spitsbergen, the largest and only permanently populated island of the Svalbard archipelago in Norway. Photo courtesy of Edtya Lokas.
Hans Glacier in Spitsbergen, the largest and only permanently populated island of the Svalbard archipelago in Norway. Photo courtesy of Edtya Lokas.

Climate change lends extra meaning to the study, as the researchers note that, “the number of additional contamination sources may rise in future due to global climate changes.”

They expect that both air temperature increases and changes to atmospheric circulation patterns and precipitation intensity will all quicken the pace of contamination transport and extraction from the atmosphere.

Edtya explained that as Arctic glaciers retreat, “The radioactivity contained in the cryoconites is released from shrinking glaciers and incorporated into the Arctic ecosystem.” She said she hopes that future climate change vulnerability assessments of the Arctic to pollution consider cryoconite radioactivity.

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Organisms on Glacier Surfaces May Function as Carbon Sinks

A new study shows that life processes of microbes living on the surface of glacier ice–organisms known as supraglacial microbes–may have an impact on the melting of glacial ice and on global greenhouse gas levels. It documents a previously unrecorded process by which these microbes produce compounds which retain carbon on the glacier surface, rather than releasing it into the atmosphere.

Forni and other glaciers in the Italian Alps (source: Viola Sonans)
Forni and other glaciers in the Italian Alps (source: Viola Sonans)

Since 2009, Dr. Andrea Franzetti, an environmental microbiologist at the University of Milan, and a team of Italian scientists have used DNA sequencing to determine the taxonomic characteristics of bacteria and algae from glaciers in several regions of the world, and to infer their metabolic processes.  Their latest work, Light-dependant Microbial Metabolisms Drive Carbon Fluxes on Glacier Surfaces, was published in The ISME Journal, a multidisciplinary journal of microbial ecology,  in April of 2016.

Dr. Franzetti and his colleagues who studied microbes dwelling on the surface of glacier ice hypothesize that the supraglacial microbes determine whether glaciers can on average absorb or release atmospheric carbon dioxide (CO2), a major greenhouse gas. Since roughly 10% of the Earth’s surface is covered by glaciers, ice sheets and sea ice, the cumulative impact of supraglacial microbes on global CO2 levels could have a significant effect on global climate.

The key issue whether the supraglacial microbes are predominantly CO2 consumers, like plants, or producers, like animals. The balance of these two types of microbes determines whether the world’s ice surfaces produce more CO2 than they absorb–or vice versa.

Although “it is still an open question,” said Dr. Franzetti during an interview with GlacierHub, he stated there is a trend that implies that marginal glaciers at the edge of ice sheets and mountain glaciers are dominated by CO2 producers and tend to act as carbon sources, while the interior regions of glaciers and ice sheets have mostly CO2 consumers and act as carbon sinks. The rates of production and absorption, multiplied by the areas where these activities are found, will determine the net effect of these organisms.

Schematic of psbD photosynthesizing gene, found in cryoconite algae (source: Curtis Neveu)
Schematic of psbD photosynthesizing gene, found in cryoconite algae (source: Curtis Neveu)

Their research in two sites–Forni in the Italian Alps of Italy and Baltoro in the Pakistani Karakoram–shows a number of biochemical processes that contribute to the production of organic molecules, removing carbon from the atmosphere. In particular, they find that organisms can process the carbon monoxide (CO) that is formed as sunlight breaks down organic matter in cryoconite (a mixture of dark sediment and microbes found on ice surfaces), turning it into compounds that remain on the glacier surface. Their sequencing techniques have documented the presence of a number of genes that support photosynthesis. The discovery of this carbon sink is a key contribution of their research. 

Since the type of microbes found on glaciers are predominantly the same as those found on ice sheets, Dr. Franzetti hypothesizes the most common metabolism is determined by the area of the ice and the availability of nutrients.  Mountain glaciers and marginal glaciers have a more confined surface area and tend to have more organic compounds from windblown sediment and upstream melt water.  Thus, marginal and mountain glaciers can support a greater number of CO2 producers than other areas of the glacier or ice sheet.

In addition to influencing the trapping or releasing of atmospheric CO2, microbial activity may lead to the darkening of the glacial surface and the reduction of the glacier’s albedo, or solar reflectivity, which leads to increased melting.  Glacial darkening can originate from various microbial activities.  These include the natural pigmentation, or color, of algae on bare surface ice, and the buildup of cryoconite.

Many supraglacial microbes produce an adhesive substance that trap sediment carried by wind and melt water.  Over time, the fine sediment and microbes coalesce into larger cryoconite granules, which are more resistant to displacement.  The dark cryoconite is able to absorb more heat from solar radiation than bare ice and causes more melting around the granule.  This process commonly creates what is known as cryoconite holes.  As the ice around the granules continues to melt, an impression is made in the ice surface, which allows for a greater accumulation of sediment in the growing hole and further melting. 

Air bubbles found in ice within cryoconite holes (source: Alean, Hambrey/swisseduc)
Air bubbles found in ice within cryoconite holes in the Italian Alps (source: Alean, Hambrey/swisseduc)

The accumulation of cryoconite is not the only way microbial activity can lead to the darkening of glacier ice. Past studies of supraglacial microbes found several species of algae that exist on bare ice, outside of the cryoconite deposits.  In order to combat the often lethal amounts of solar radiation that the algae are exposed to on bare ice, they release dark colored pigments.  Not only does this dark pigment allow the algae to withstand the high level of solar radiation, it also promotes surface melting.  A larger amount of melt water increases the available habitat of the algae and can lead to greater glacial darkening and melting. 

Although several studies show microbial activity does lead to glacial darkening and melting, Dr. Franzetti stated, “[The] assessment of the relative contribution [to darkening the glacier] of biological processes, chemical processes [normal sediments and geologic processes] and anthropogenic processes is controversial.”  It is unclear how much glacial melt is actually attributed to the microbial darkening.

Glacial ice is a major component of global climate.  As studies on supraglacial microbes continue to reach publication, it is becoming apparent that bacterial and algae activity has an influence well beyond the surface of the ice.

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Roundup: Fewer Hikers, Less Pollen, More Algae on Glaciers

Each week, we highlight three stories from the forefront of glacier news.

New Zealand Glaciers Banned Hiking

fox glacier new zealand gareth eyres Source:


New Zealand is renowned for its wondrous scenery, and among the country’s top tourist attractions are two glaciers that are both stunning and unusual because they snake down from the mountains to a temperate rain forest, making them easy for people to walk up to and view.

The hot weather has even created a new type of tourist attraction over the other side of the mountains. Purdie said the glaciers there are also rapidly retreating, resulting in tourists taking boat rides on the lakes to see some of the massive icebergs that have begun to shear away.”

Read more about this policy here.

Microalgal Community Structures in Cryoconite Holes upon High-Arctic Glaciers of Svalbard

From Biogeosciences:

Biplot for the partial RDA with glacier and place as covariables, after interactive forward-selection covariates analysis. Source: photo of article.
Biplot for the partial RDA with glacier and place as
covariables, after interactive forward-selection covariates analysis. Source: Biogeosciences.

“Glaciers are known to harbor surprisingly complex ecosystems. On their surface, distinct cylindrical holes filled with meltwater and sediments are considered hot spots for microbial life. The present paper addresses possible biological interactions within the community of prokaryotic cyanobacteria and eukaryotic microalgae (microalgae) and relations to their potential grazers, such as tardigrades and rotifers, additional to their environmental controls. Svalbard glaciers with substantial allochthonous input of material from local sources reveal high microalgal densities.

Selective wind transport of Oscillatoriales via soil and dust particles is proposed to explain their dominance in cryoconites further away from the glacier margins. We propose that, for the studied glaciers, nutrient levels related to recycling of limiting nutrients are the main factor driving variation in the community structure of microalgae and grazers.”

Read more about microalgal community structures here.

Pollen Limitation in Nival Plants of European Central Alps

From American Journal of Botany:

Taxonomic composition of the pollen load of relevant insect pollinators ( N = 10 investigated individuals per insect group). Source: photo of article.
Taxonomic composition of the pollen load of relevant insect
pollinators ( N = 10 investigated individuals per insect group). Source: Am J Botany.

” A plant is considered to be pollen-limited when—due to an insufficient supply with pollen of adequate quality—the seed output remains below the potential value. Pollen limitation is thought to be a general phenomenon under the harsh climatic conditions at high latitudes and elevations.

Our study in the alpine–nival ecotone revealed that insect activity is not a limiting factor for pollination success in the studied plant species, which can be explained by the fact that anthesis functions and pollinator activity are largely coupled. ”

Learn more about pollen limitation here.

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The Microscopic Life of Glaciers

Svalbard Glacier, courtesy of Airflore/Flickr.
Svalbard Glacier, courtesy of Airflore/Flickr.

Though it can be hard to imagine that cold, barren-looking glaciers are conducive to life, glaciers are actually teeming with organisms. Glacier surfaces are filled with cylindrical holes called cyroconite holes, in which melt water accumulates and micro-algae and cyanobacteria  thrive.

Now, a new study published in Biogeosciences has taken a closer look at these complex ecosystems to better understand the interactions between the organisms that inhabit this icy space. They found that Svalbard glaciers that received large quantities of deposits from local areas tended to have large amounts of microalgae. These microalgae can create large colonies to protect them from invertebrate grazers like tardigrades, minute animals also known as water bears, and other microscopic animals like rotifers and ciliates. Large microalgae colonies can protect themselves from the filtration feeding strategy used by rotifers.

The researchers studied these mini-ecosystems on four glaciers in Svalbard, a Norwegian Archipelago. Each sample had a different level of exposure to nutrients, water depth and the degree to which the cyroconite holes were isolated so that the researchers could separately analyze the effects of environmental factors and other biological interactions, such as animals grazing on the microalgae.

Under a microscope, the researchers identified the different species of tardigrades and rotifers. They also measured the density of microalgae clusters and the types of microalgae and cyanobacteria.

Colony of rotifers, courtesy of Specious Reasons/Flickr
Colony of rotifers, courtesy of Specious Reasons/Flickr

In glaciers farther away from glacier-free land, the microalgae species differed from glaciers closer to land. Species variability could be attributed to wind transport, the researchers suggest.

“We propose that selection occurs because polar cyanobacteria are often associated with dust in soil, and thus easily transported by 20 wind,” they wrote. Levels of nitrogen deposits from bird guano and tundra may also play a role in determining which species of microalgae lived where, but the researchers felt this factor was less important than wind transportation.

The species and quantities of grazers, on the other hand, did not vary much from site to site. Grazer types were also correlated with the types of microalgae found in different cyroconite holes. Rotifers tended to live around Zygnemales and Chlorococcales, while tardigrades were usually found around larger Zygnemales.

“The high abundances of tardigrades, rotifers, and ciliates, including genera with different feeding strategies, have been found and suggest a complex food web between more trophic levels than measured in the present study,” the authors wrote. “Feeding experiments and analysis of stomach contents may help to bring a more detailed picture of this yet hardly known food web.”

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Photo Friday: Cryoconites and Glacier Tables

Have you ever seen dark cavities on glaciers, which are also referred to as “cryoconites”? These holes, which can be meters deep,are created from debris on top of glaciers. Dark-colored debris, including soot, dust, and pollen, speed up the melting process of glacial ice as a consequence of their low reflectivity to incoming sunlight. In some cases, glacial surface debris can also form pits in the ice through chemical melting. Hence, most of the glacial thaw holes are filled with melt-water, which become home to cyanobacteria, fungi, and other microbes. However, some large solid debris, in particular boulders, will prevent the ice beneath from melting as surrounding ice, forming glacier tables. Here are some photographs of cryoconites and glacier tables.

Learn more about glacial surface debris here.

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Glacier Melting Sets Free Organic Carbon

Research has shown that glaciers have a greater role than was previously known in the movement of organic carbon into and through aquatic ecosystems, including the oceans. Organic Carbon (OC) refers to carbon contained in organic compounds that is originally derived from decaying vegetation, bacterial growth, and metabolic activities of living organisms. It serves as a primary food source for marine organisms, particularly microbes. In addition, it contributes to the acidification of water. Particularly in freshwater ecosystems, excessive OC can result in a brownish coloration. In fact, the amount of OC is often used as an indicator of overall water quality.

Figure 1. Location of glacier DOC samples classified by type. a–d, Samples were collected from a wide variety of glacial environments including: Alaska (a), Tibet (b), Dry Valley glaciers in Antarctica (c), and the Greenland Ice Sheet (d). (Source: Hood et al.)
Figure 1. Location of glacier DOC samples classified by type. a–d, Samples were collected from a wide variety of glacial environments including: Alaska (a), Tibet (b), Dry Valley glaciers in Antarctica (c), and the Greenland Ice Sheet (d). (Source: Hood et al.)

A recent research shows that the increase in glacier runoff through melting and iceberg calving has led to a rise of OC flux entering marine and lacustrine ecosystems, and this flux is expected to grow in the coming decades. According to the article, glacier ecosystems accumulate OC from primary production on the glacier surface, particularly in cryoconite deposits, and also from the deposition of carbonaceous material derived from terrestrial and anthropogenic sources.

To quantify the total storage of OC in terrestrial ice reservoirs, the study integrates measurements of organic carbon from mountain glaciers, ice sheets in Greenland, and Antarctica Ice Sheet, with data from locations that span five continents (see Figure 1). It turns out that that largest amount of OC is located in Antarctica, followed by Greenland and mountain glaciers. However, it is found in the study that a large portion of the OC released from melting glaciers is from mountain glaciers and peripheral glaciers which exit from the Greenland ice sheets (see Figure 2). The surprisingly disproportionately high DOC export from mountain glaciers and Greenland is associated with their glacier mass turnover rate, which is higher than in Antarctica. Even as glaciers are losing ice through melting and caving at their lower ends, they continue to receive new snow at the top, which converts to ice—a process of flow, which contributes to the movement of OC through the glaciers.

Figure 2. Storage and flux of glacier DOC. Total glacier storage of DOC (a) and annual DOC export in glacier runoff (b) for MGL, GIS, and AIS.
Figure 2. Storage and flux of glacier DOC. Total glacier storage of DOC (a) and annual DOC export in glacier runoff (b) for AIS (Antarctic Icesheet), GIS (Greenland Icesheet) and MGL (mountain glaciers). (Source: Hood et al.)

Dissolved organic carbon (DOC) and particulate organic carbon (POC), two major components of the OC, are both significant components in the carbon cycle, because they are primary food sources in aquatic food webs. In particular, DOC forms complexes with trace metals, which can be transported and consumed by organisms. This may have drastic affects on marine life, “because this material is readily consumed by microbes at the bottom of the food chain,” said U.S. Geological Survey research glaciologist and co-author of the research Shad O’Neel. The microbes are an important source of food for plankton and for larger organisms in the seas, including crustaceans and fish.


Iceberg Calving (Source: Flickr/Indistinct)
Iceberg Calving (Source: indistinct/Flickr)

The study raises questions of the implications of OC input for carbon dioxide concentration in atmosphere. The authors suggest that glacier-derived OC shows a high degree of biological availability, when compared to other terrestrial sources. Hence, it is more likely to result in more rapid decomposition of dead marine organisms, which otherwise would fall from upper zones of the oceans to deeper sections, where they would remain for long periods. This decomposition, in turn, contributes to carbon dioxide outgassing from the oceans to the atmosphere.

For another story about the effects of glaciers on ocean chemistry and ecology, look here.

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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.


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.

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