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Exploring cyanobacterial diversity in Antarctica Blog

4 Posts tagged with the microbial_mat tag
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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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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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