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Exploring cyanobacterial diversity in Antarctica Blog

17 Posts tagged with the cyanobacteria tag
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This afternoon we went for a walk on the Lake Fryxell. The ice is incredible clear in the moat regions, and one can find everywhere cyanobacterial mats frozen into the ice. These cyanobacterial mats were originally from the bottom of the lake, and are called lift-off mats. Microbial mats often drift to the top of the water when they are pushed upwards through the formation of gas bubbles. Although mats are now frozen, it is very likely that many of the cyanobacteria in the mats are still viable.

 

Lake Fryxell with Canada Glacier in the background

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Dried cyanobacterial mats in the ice

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It is November 2012 and it is time to head back to Antarctica. This year we are a team of researchers and students from University of Canterbury (NZ), UC Davis (USA) and the Natural History Museum, London. We are coming from the research areas of Microbial Biodiversity, Microbial Ecology and Geobiology. We will be working in the McMurdo Dry Valleys and study the benthic biology of Lake Fryxell and Lake Vanda. In total, we will be in Antarctica seven weeks, two weeks at Lake Fryxell and three weeks at Lake Vanda, which is very exciting !

 

Cyanobacteria-based microbial mats and microbialites cover large parts of these lakes. The lakes are ice-covered and meromictic with a stratified water column, which makes them very interesting systems to study how environmental conditions affect microbial diversity and community composition and microbialite morphologies and their assemblages. The microbial communities will be collected by divers ( ...not me but the other members of my team). They will also characterise the different shapes of microbialite structures, as well as light conditions and photosynthesis activity of the lake environment.   We will also do light microscopy to study the cyanobacterial morphotype diversity.

 

Lake Fryxell at night

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Most of the cyanobacterial mats that we have found were orange pigmented and the macroscopic structure was flaky to cohesive. The orange colour is due to carotenoids which are an protection against UV and oxidative stress.

 

I had a small light micrscope with me in the field and the genus Leptolyngbya dominated the orange mats. Leptolyngbya are filamentous non-branching cyanobacteria belonging to the order Oscillatoriales. They are mostly between 0.5-3 micrometre thick. However, the lower side of the orange layers sometimes had green pigmentation, which besides the Leptolyngbya also had some Phormidium. The genus Phormidium also belong to the order Oscillatoriales, but they are thicker with a width of around 5 micrometres.

 

   Flaky orange-pigmented cyanobacterial mats dominated by Leptolyngbya

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Cohesive orange-pigmented cyanobacterial mats

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green lower side of cyanobacterial mat with Phormidium

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Interestingly, we also found some cyanobacterial mats which were dark purple to black. This colour is due to the UV-screening Scytonemin. We found the genus Schizothrix sp. (Oscillatoriales)  in the mats which is known to produce Scytonemin. We also found several ponds with large accumulations of the genus Nostoc, which belongs to the order Nostocales and has specialist cells called heterocysts for nitrogen-fixation.

 

Cyanobacterial mats with the Scytonemin-producing genus Schizothrix

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Nostoc accumulations in a meltwater pond

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We also found a few ponds with green algae. Green algae biofilms are easy to distinguish from cyanobacteria as green algae are very bright green.

                                                                                              

Green algae

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The Wright Valley is one of the ice-free Dry Valleys. The Upper Wright valley is characterised by the so-called Labyrinth, which is an area of steep-sided canyons and channels. It is mainly dolerite and most rocks are bright red. Based on the literature it was formed by large 'floods during the mid-Miocene era'.

 

The Labyrinth

 

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In the area you can find many strangely shaped rocks. They are called ventifacts, and are wind- and dirt-sculpted rocks.

 

Ventifacts in the Labyrinth

 

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Wherever you look you only see rocks and it often reminded me of images showing how it may look on Mars.

 

 

Landscapes like on Mars

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However, there is life. On one of our walks, we found these lichens. They were on the top of one of the ridges, where the overall humidity seems to be higher due to its location at a height of greater than 750 metres, and the greater influence of clouds and fog. Many of the lichens grow under or in cracks of the rocks, and this enhances the erosion of the rocks.

 

 

Lichens on rocks in the Labyrinth

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AND, as soon as you get running water and temporary ponds you get thick accumulations of orange-pigmented mats. To date there have only been few morphological descriptions and there is no DNA-based data available at all.

 

 

Meltwater ponds covered by ice with bright orange mats

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Orange cyanobacterial-based microbial mats

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Close-up of microbial mat

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There are many small ponds and lakes at Cape Evans, similar to Cape Royds . After a quick survey of the ponds, we concentrated on five ponds for sampling. We sampled for morphological, DNA- and RNA-based analysis of the cyanobacterial diversity, as well as nutrient analysis of the water.

 

In one pond we found a pink coloured layer at the bottom of the mats, which is due to the presence of purple bacteria that  are anoxygenic phototrophs.


 



Cyanobacterial mats in Skua Lake

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Large cyanobacterial mat accumulations

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Cyanobacterial mat with a pink layer of purpil bacteria  at the bottom



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Water sampling at a small pond at Cape Evans


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Today, we went to Cape Evans, where the famous hut from the Terra Nova Expedition is located. The helicopter flight took 20 minutes and it was spectacular with great views over the the McMurdo Ice Shelf and sea ice. A group of conservators from the Antarctic Heritage Trust has been spending the whole summer here to work on the famous hut. They have a cosy camp with a communal kitchen and dining hut and several polar tents. Actually, these kind of tents were also used by Scott and their design has only little changed since then. They are can withstand stronger winds than mountain tents. From our lunch break we had a great view on Scott’s hut . After we were done with our sample collection the conservators from AHT showed us the hut.


Flight over the ice

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Polar tents at Cape Evans

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Scott's hut  build during the Terra Nova Expedition

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Conservation work at the hut by Antarctic Heritage Trust

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Yesterday we sampled cyanobacterial mats and water samples on the McMurdo Ice Shelf. We went for the day to an area near Bratina Island. In this area, the ice shelf  is covered with a  layer of sediment and hundreds of meltwater ponds can be found. During the summer they forms a large network of meltwater ponds  and it has the most extensive microbial growth and largest non-marine biota in southern Victoria Land. It  has been suggested that the  area plays an important role as  source for inocula through dispersal by winds into the more extreme regions such as the Dry Valleys.

 

Although some of the ponds are only several meters away from each other , they can have very different characteristics. A large range of salinities can be found in the area ranging from fresh to hypersaline.

 

 

 

                        McMurdo Ice Shelf and Bratina Island with Royal Society Range in the background

 

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   Temperature, conductivity and ph measurements at an hypersaline pond near Bratina Island. The pond is called Salt Pond and has thick white salt crust around the water edge.

 

 

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                                  Cyanobacterial mats with orange pigmented pinnacles

 

 

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The terrain surounding Cape Royds is covered with many ponds that vary in size, depth, shape and conductivity (salinity). There are also two larger lakes: Blue Lake and Clear lakes that are ice-covered all year. They were named during Shakleton’s expedition because of their blue and clear ice colour.  We were amazed by the variability of pond characteristics and diversity of microbial mats.



Back at the Natural History Museum we will study the cyanobacterial mats using microscopy and DNA-based tools to see if different mat types comprise different cyanobacterial communities.




                                             small pond with lift-off mats at Cape Royds

                                                 

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                                                                 Cyanobacteria-dominated mats

    

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One of the aims of the field event is to collect cyanobacteria from locations where the scientists of Scott’s and Shakleton’s expeditions collected material 100-years ago and compare them with the historic samples. We will sample cyanobacterial mats on Ross Island and the McMurdo Ice Shelf.


Cyanobacterial samples were collected during the three expedition:

 

1) The National Antarctic Expedition (1901-04; Discovery Expedition) led by R.F. Scott

 

2) The British Antarctic Expedition (1907-1909; Nimrod) led by E.H. Shackleton

 

3) The British Antarctic Expedition (1910-1913; Terra Nova) led by R.F. Scott

 



                                        Hut Point in front of McMurdo Station with the Discovery Expedition hut


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                                                                           Discovery Hut


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Cyanobacteria are also very common in hypolithic communities that are microbial communities growing under translucent rocks such as quartz rock. These communities can be a mixture of cyanobacteria, other bacteria, green algae, protists, mosses, lichen and fungi.

It is still very little known about these hypolithic communities. As environmental conditions in Antarctica are extreme scientists believe that hypolithic habitats can provide some protection from high UV radiation and rapid fluctuation of freeze-thaw processes. The Dry Valleys are cold deserts with very limited liquid water and hypolithic rock habitats provide an increased water availability through water condensation processes on the rock surfaces.

                                                  Quartz rock

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                                       Below the same quartz rock    

The green spots on the bottom of the rock are cyanobacterial communities  

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                  Green hypolithic community growing around the bottom of a small quartz rock

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Today we went to an area that is classified as Antarctic Specially Protected Area or ASPA. These are sites that are of special historic or ecological significance and a permit is required for entry.

 

The area comprises sloping ice-free ground with summer ponds and small meltwater streams draining from the Canada Glacier to Lake Fryxell. It is  is on the other side of the Canada Glacier and  the hike took ca 1.5 hours including the crossing of Canada Glacier.

 

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The Canada Glacier stream area has high biomass accumulations in comparison to most other regions of the Dry Valleys. Several moss species (Bryum argenteum, Hennediella heimii and Bryum pseudotriquetrum), lichens (Lecanora expectans, Caloplaca citrina) and freshwater algae (Prasiola calophylla, Tribonema elegans) have been described from the stream area (Management Plan for Antarctic Specially Protected Area No. 131).

 

         

                                                                                                      Canada stream and Lake Fryxell

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Cyanobacterial mats are also abundant. Oscillatoria, Leptolyngbya, Phormidium, Calothrix, Nostoc and Gloeocapsa are the common cyanobacterial genera the mats growing in the streams.

 

 

                                                                                                   Cyanobacerial mats

 

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                                                                                       Nostoc and other cyanobacteria growing on moss

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In Lake Hoare the mats are vertically stratified. Each year one layer is formed and they can be used as indicators of growth and environmental conditions just like tree rings. Similar to microbial mats in other lakes the layers have different pigmentations for light capturing and protection.

 

                                                                                Cyanobacterial mats in Lake Hoare

 

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After the divers had brought up mat samples from a depth of ca 10 m, we went back to the lab and identified the diversity using light microscopy. The microbial mats contained different cyanobacteria including the genera Oscillatoria, Phormidium, Leptolyngbya and Nostoc.

 

After returning to the Natural History Museum, we will carry out DNA-based methods to characterise their evolutionary relationship to other Antarctica cyanobacteria.

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Boulder Pavement (77.5227°S, 161.7466°E) is an area ca 1.5 hour hike from the Lake Vanda along the Onyx River. It is the most extensive area of microbial mats in the Wright Valley. When I visited the area it was still too early in the season to have  water running or much growth of microbial mats.

 

However, i was able to find one spot where the ice had melted and bright orange microbial mats were visible. The orange colour is due to carotenoids, pigments that protect the cyanobacterial cells from UV radiation and reactive oxygen species.

 

Orange-pigmented cyanobacteria-dominated mats

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Dried river bed near Boulder Pavement

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The lake floor is covered with cyanobacteria-dominated mats of different thickness. The microbial mats from 59 ft are ca 1 cm thick and have small pinnacles growing out off the flat mats. The cross-section show differently coloured layers with a brown layer on top and a green and purple layer below (the colours are difficult to see under the yellow coloured light of our science tent). The different colours are due to the production of  pigments for efficient uptake of light.

 

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The objectives of our project are to study the cyanobacterial mats and microbial structures in Lake Joyce to better understand the diversity and processes that create these microbial structures.

 

In order to study the structures the samples need to be collected by  diving. Once they are brought back to our field lab directly on the ice of Lake Joyce, they are documented, the diversity studied using microscopy and samples preserved for further analysis back at our home institutions. I am particularly interested in collecting material for DNA-based tools to study cyanobacterial diversity.

 

 

Diving in Lake Joyce

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Microscopy analysis of cyanobacteria from Lake Joyce

 

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Filtration of water samples

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