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During the first week of our trip, we made an exciting discovery! In one of the ponds in Maiviken Cove, we found cyanobacterial mats.

 

Maiviken is a a beautiful cove on Thather Peninsula,only a 1 hour walk away from KEP. The cyanobacterial mat were in a small pond close to the scree slopes on the eastern side of the valley. The cyanobacterial-based mats were a lot more gelatinous than, for example, mats from the McMurdo Ice Shelf, but nevertheless clearly definiable as lift-off mats of up to 1 cm thickness.

 

Back in the lab, I had a look under the microscope and the mats were comprised of various morphotypes of Oscillatoriales includig Phormidium and Leptolyngbya, the unicellular order Chroococcales as well as Nodularia, which is a genus in the nitrogen-fixing order Nostocales.

 

A few weeks later, I also found cyanobacterial mats with a similar taxa composition in apond in Hapon Bay, which is also on Thather Peninsula. This finding is interesting as there is very little know about mat-forming cyanobacteria from South Georgia. Therefore, we collected material for more detailed microscopic and DNA analyses of the cyanobacterial diversity in these mats.

IMG_8116.jpgCyanbacterial mats in Maiviken Cove

 

On Barff Peninsula, I found a meltwater stream where the cyanobacterial genus Nostoc was growing on some of the rocks. The Nostoc nodules were ca 1 cm in diameter. It was difficult to get a good image beause of the reflection of the sun in the fast flowing water.

IMG_8398.jpgNostoc in a stream on Barff Peninsula

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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

Cyano1.jpg

 

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

Cyano5.jpg

 

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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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.

 

                                                                             Canada_glacier.jpg                                             

 

 

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

                                                                                stream.jpg

 

 

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

 

                                                                                 Mat.jpg

 

                                                                                       Nostoc and other cyanobacteria growing on moss

                                                                                     moss.jpg

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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

 

                                                                      LHmat1.jpg

 

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.