CR
Cryospheric Sciences

microbes

Image of the week – Micro-organisms on Ice!

Image of the week – Micro-organisms on Ice!

The cold icy surface of a glacier doesn’t seem like an environment where life should exist, but if you look closely you may be surprised! Glaciers are not only locations studied by glaciologists and physical scientists, but are also of great interest to microbiologists and ecologists. In fact, understanding the interaction between ice and microbiology is essential to fully understand the glacier system!


Why study micro-organisms on glaciers?

Micro-plants, micro-animals and bacteria live and reproduce in cryoconite ecosystems on the surface of glaciers. Cryoconite is a dark coloured material (Fig. 2) found at the bottom of cylindrical water-filled melt holes (cryoconite holes) on a glacier surface; it consists of dust and mineral powders transported by the wind, and micro-organisms. Cryoconite holes are formed as the dark coloured material causes localised melting, due to reduced albedo (ability of a surface to reflect solar energy).

Figure 2: Example of a Cryoconite hole filled with dark cryoconite material (markers are 10×10 cm) [Credit: Tommaso Santagata – La Venta Esplorazioni Geografiche]

Because organisms in cryoconite thrive in extreme conditions, they are very unique and interesting to study. Information about their genetic makeup and chemical structure can help to inform, for example, medical and pharmaceutical sciences. Currently, however, information on their community structure is still limited.

Cryoconite ecosystems are very isolated and must work together to survive and thrive. Some micro-organisms (e.g. micro-algae) can photosynthesise and are able to live autonomously inside cryoconite holes using atmospheric carbon dioxide, sunlight, water and chlorophyll. By this same mechanism, they can find all the molecules essential for their vital and structural needs and consequently they generate most of the molecules necessary for all other living things. For example, the waste product of photosynthesis, oxygen, is essential for the survival of all organisms living in aerobiosis in these communities. Due to their key role in the ecosystem, the micro-algae are known as “primary producers”.

As around 70% of the earth is covered in water, which is colonised by micro-algae, studying the way they survive in extreme conditions and how they contribute to the ecosystem is of global importance – especially at this time of climate change.

The diversity of highly active bacterial communities in cryoconite holes makes them the most biologically active habitats within glacial ecosystems.

Data collections – Six days on THE glacier

The Perito Moreno glacier (Fig. 3) is known as one of the most important tourist attraction in Argentinian Patagonia (see our previous IOW post). Each day, hundreds of people observe the impressive front of this glacier and wait to see ice detachments and hear the loud sound of it’s impacts in the water of Lake Argentino. The glacier takes it’s name from the explorer Francisco Moreno, who studied the Patagonian region in the 19th century. The glacier is more than 30 km in length and an area of about 250 km2, Perito Moreno is one of the main outlet glaciers of Hielo Patagonico Sur (southern Patagonia icefield).

Figure 3: Aerial view of the Perito Moreno
[Credit : Tommaso Santagata – La Venta Esplorazioni Geografiche]

In April 2017, after several missions to the Greenland Ice Sheet to study extremophilic micro-organisms (organism that thrive in extreme environments) of ice, a team of Italian and French scientists organised a scientific expedition to study the microbiology of Perito Moreno. The expedition was organised by La Venta and Spélé’Ice and included researchers from several French and Italian Universities (see below for full list)

Perito Moreno is very well known, especially to the La Venta team, who have been organising scientific expeditions in Patagonia since 1991. The microbiological research objectives of this mission were to study the micro-organisms that live on the surface of Perito Moreno and compare them to results obtained in the other polar, sub-polar and alpine regions. The multi-disciplinary research team were able to set up a complex field laboratory, which included a microscope and an innovative small tool size capable of DNA sequencing. This meant that samples could be analysed immediately after their extraction from the ice (Fig. 1).

Getting all the equipment and personnel to achieve this expedition onto the ice was not an easy task. The team and their equipment were transported by boat to a site near the front of the glacier. Equipment then needed to be transported to the Buscaini Refugee, a shelter used as a base-camp by the team (Fig. 4). This took two trips, on foot, of about 7 hours (12 km of trail along the lateral moraine and the ice of the glacier with very heavy backpacks) – not an easy start! Luckily this hardship was somewhat mitigated by the absence of extreme cold, in fact, abnormally hot weather tallowed the team to move and work in t-shirts – not bad!

Figure 4: Walking into the field site along the ice of Perito Moreno – part of the 12km of trail to the Buscaini Refugee shelter
[Credit: Alessio Romeo – La Venta Esplorazioni Geografiche]

Thanks to these favourable weather conditions, all the goals were achieved in the short amount of time the team were allowed to camp on the glacier (special permission is needed from the national park to do this). During the five days of activity, many samples were taken and sequenced directly at the camp by the researches. Other important goals, such as morphological comparisons and measurements of the velocity of the glacier through the use of GPS, laser scanning and unmanned aerial vehicles were achieved by another team of researchers (stay tuned for another blog post about this!).

Universities and research institutes involved: University Bicocca of Milan – Italy, University of Milano – Italy, Sciences of the Earth A.Desio – Italy, Natural History Museum of Paris – France, University Diderot of Paris – France, University of Florence – Sciences of the Earth – Italy, University of Bologna – Italy.

Further Reading

Edited by Emma Smith


Tommaso Santagata is a survey technician and geology student at the University of Modena and Reggio Emilia. As speleologist and member of the Italian association La Venta Esplorazioni Geografiche, he carries out research projects on glaciers using UAV’s, terrestrial laser scanning and 3D photogrammetry techniques to study the ice caves of Patagonia, the in-cave glacier of the Cenote Abyss (Dolomiti Mountains, Italy), the moulins of Gorner Glacier (Switzerland) and other underground environments as the lava tunnels of Mount Etna. He tweets as @tommysgeo

Image of the Week — Microbes munch on iron beneath glaciers

Image of the Week — Microbes munch on iron beneath glaciers

The interface between a glacier and its underlying bedrock is known as the subglacial zone. Here lie subglacial sediments, the product of mechanical crushing of the rock by the glacial ice. Despite their lack of sunlight, nutrients and oxygen, subglacial sediments host active and diverse communities of microorganisms.

What we (don’t) know about subglacial microorganisms

The past few decades have seen major advances in our understanding of these communities, including the role these microbes play in the chemical breakdown of underlying bedrock (chemical weathering reactions). It is now known, for example, that microorganisms in subglacial systems are involved in pyrite oxidation and it certainly seems that bedrock mineralogy influences the composition of these microbial communities.

However, most studies to date have focussed on the biogeochemical cycling of sulfur and nitrogen in these systems. Consequently, the microbial mediation of iron cycling in subglacial systems remains poorly understood, despite the importance of iron in ocean fertilisation and other downstream environments. For instance, phytoplankton in the open ocean are often limited by the amount of iron available, so fluxes of iron to the oceans from glaciers and ice sheets are an important contribution to ocean productivity.

A new study about subglacial iron

In a new paper published in Biogeosciences, we investigate microbial iron reduction in subglacial sediments. Microorganisms that carry out this metabolism are able to harness energy from the reduction of oxidised iron minerals (such as ferrihydrite and other iron oxides).

We wanted to know two things:

  1. are these microorganisms present and alive in subglacial sediment?
  2. are these microorganisms adapted to the cold conditions of these environments?

 

To achieve this, we set up experiments in which we ‘teased out’ the microorganisms that make a living from iron reduction, and measured their rates of iron reduction at two different temperatures: 4°C (blue line in the figure) and 15°C(red line). These temperatures were chosen since truly cold-loving (‘psychrophilic’) microorganisms grow optimally at temperatures below 10-15°C, whereas those that tolerate cold temperatures (‘psychrotolerant’) prefer to grow in higher temperatures.

Microorganisms that can use iron to make a living are amongst the most plausible life to exist on Mars

We found that active iron-reducing microorganisms were present in all of our subglacial sediment samples, which spanned glaciers in the High Arctic, European Alps and Antarctica, and that in almost all cases rates of iron reduction were higher at the lower temperature tested. To get an idea of which microorganisms were carrying out this process, we looked at the DNA from our experiments to identify the microbes present. We found that the microorganisms using iron in our experiments were largely the same, suggesting that the same key players are active in these types of environments worldwide. Overall our paper suggests that microbial iron reduction is widespread in subglacial environments, with implications for the availability of iron for other biogeochemical processes downstream. Subglacial environments are thought to be similar to potentially habitable environments on Mars, and microorganisms that can use iron to make a living are amongst the most plausible life to exist on the Red Planet, now and in the past. Our work therefore strengthens the hypothesis that similar environments beyond Earth could harbour this type of life.

Edited by Sophie Berger


Sophie Nixon is a postdoctoral researcher in the Geomicrobiology group at the University of Manchester. She completed her PhD in Astrobiology in 2014 at the University of Edinburgh, the subject of which was the feasibility for microbial iron reduction on Mars. One essential task in the search for life on Mars and beyond is defining the limits of life in extreme environments here on Earth. It was during her PhD that this study was carried out in collaboration with researchers at the University of Bristol, where Sophie gained her MSci in Geographical Sciences. Sophie’s research interests since joining the University of Manchester are varied, spanning the microbiological implications of anthropogenic engineering of the subsurface (e.g. nuclear waste disposal, shale gas extraction), as well as life in extreme environments and the feasibility for life beyond Earth. 

Image of the Week – Blood Falls!

Image of the Week – Blood Falls!

If glaciers could speak, you might imagine them saying – “HELP!” The planet continues to warm and this means glaciers continue to shrink. Our new image of the week shows a glacier that appears to be making this point in a rather dramatic and gruesome way – it appears to be bleeding!


If you went to the snout of Taylor Glacier in Antarctica’s Dry Valley region (see map below) you would witness a bright red waterfall, around 15m high, flowing from the glacier into Lake Bonney. Due to it’s colour, this waterfall has acquired the somewhat graphic name: Blood Falls!

The Dry Valleys

Location of Taylor Glacier in Taylor Valley – one of the Antarctic Dry Valleys. The American McMurdo Research Station is located a short distance away [Credit: USGS via Wikimedia Commons ]

The dry valleys, as the name suggests, are considered one of the driest and most arid places on Earth – which seems like an unusual location for waterfall! The area is completely devoid of animals and complex plants, however, in finding an explanation for the colour of Blood Falls, scientists have also gained an insight into a whole ecosystem hidden beneath the Dry Valley glaciers.

Why is the water red?

The water that feeds Blood Falls is salty and rich in iron. This water is forced out from underneath the glacier by the pressure of the overlying ice (see schematic below) and as it emerges the iron in the water comes into contact with oxygen causing it to rust (oxidise) and turn the water red. But why is this water so salty and iron-rich in the first place? The story of how this unusual water came to be starts around five million years ago…

At this time, it is thought that the dry valleys were submerged beneath the ocean as part of a system of fjords (Mikucki et al., 2015). Subsequent uplift of this land and climatic cooling causing a drop in sea level left some of this salty ocean water isolated as a lake. Around 1.5 million – 2 million years ago a glacier started to form on top of this lake. The ice cut the lake off from the atmosphere and caused the lake water to become even more salty by the process of cryoconcentration (lake water in contact with the glacier ice is frozen, the salt is left behind in the lake increasing the concentration). Iron was introduced into the water from the bedrock beneath the lake, which was ground up as the ice moved over the top of it. There was also something else in this ancient sea water, that surprised scientists when they began to analyse the water from Blood Falls – microbes!

A schematic cross-section of Blood Falls showing how microbial communities survive in this hostile environment [Credit: Zina Deretsky, NSF ]

Life in the lake – Microbes

When it was covered in ice, this subglacial lake was very cold and cut off from the out side world – meaning no sun light and oxygen, which are normally essential for microbes to survive. However, the microbes in this lake are thought to have adapted to survive using sulphates and iron in the water (Mikucki et al., 2009).  This strange ecosystem is surviving in extreme conditions and shows how adaptable microbes can be. An area once thought to be too inhospitable to support much life has been shown to be much more “lively” than first thought – sparking up ideas about lifeforms in other inhospitable environments, such as Mars.

Further Reading

 

Edited by Sophie Berger

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