This year, we went back to Lake Joyce to study the benthic biology in the McMurdo Dry Valleys. The 3D microbial structures that are growing out of the mat are particularly interesting because most of them have a calcite skeleton. This is the only lake in the Dry Valleys where microbial mats have such distinctive calcite skeletons.

The calcite skeleton makes these microbialites particularly interesting for geobiology, where modern microbial mats are studied to enable a better interpretation of microbialite fossils from early Earth. 

Over the last three weeks we collected samples that will allow us to investigate if the water chemistry, light and sedimentation effect the growth of microbialites in the lake. We also collected mat material to carry out DNA and microscopy analysis to evaluate the role that cyanobacteria, other bacteria and eukaryotes play on the formation of microbialites and their calcite skeleton.

Microscopy image of Phormidium cyanobacterial filaments in Lake Joyce mats. Most of the Phormidium filaments have a strong purple pigmentation though the production of Phycoerythrin for a better utilisation of the limited light that is available in Lake Joyce.

Anne working at the microscope.

Close-up image of microbialites with calcite skeleton covered by thin microbial mat webs .

Microbialite structures with calcite skeleton collected from Lake Joyce by diving.

The team getting ready for a dive to collect microbial mats.

The main efforts of the field event led by researchers from UC Davis, California, were to map the distribution of the microbial structures in the lake and to test what the influence of sedimentation is on the microbial structures.

The imaging is done by a drop camera that is held on a rope through a hole in the ice. The team installed several traps in the ice that will collect sediment from now until next season.Each hole is individually drilled with a jiffy drill in order to insert the traps and document the microbial mas and microbial structures.

The team drilling a hole in the ice.

This year, we will be be out in the field for 5 weeks. Our first camp is at Lake Fryxell. During our time at Lake Fryxell, we will be able to use the facilities by the US Antarctic Programme, which is pretty cool! The camp consist of a James Way as living area with heating, internet and even a telephone line to Scott Base and McMurdo. We sleep in tents but spend most of the day out on the lake or in the labs and hut.

Lake Fryxell camp

Inside the hut

Our drinking water is melted glacier ice

Snack corner

Frozen Veggies

Camping at Lake Fryxell

My tent

Solar  energy

Wind energy

Life in Lake Joyce is dominated by microbes. The water of Lake Joyce is nutrient-depleted and only little light makes it through the ice. The nutrient concentrations are so low in the water column that microbes remain at low concentrations, however diverse microbial communities can be found a long the bottom and the sides of the lake.

Much of the microbial communities are cyanobacterial mats and many unusual structures can be found.

Some of the structures are several centimeters  tall and have  a orange-purple colour. The colour is due to the  production of cyanobacterial pigments that help capture light for photosynthesis.

I am going to Antarctica to study cyanobacteria because they are  very important for the ecology of Antarctic freshwater system such as lakes, ponds and meltwater ponds on ice shelves.

Cyanobacteria were initially described as algae in the 18th century, before scientists realised they were bacteria. Therefore, they are also called Cyanophyta or blue-green algae based on their blue-green coloration.

Antarctic cyanobacteria are generally characterised by their ability to cope with the harsh conditions of Antarctica, which include:

• low temperatures
• ice formation
• high salt concentrations
• several months of darkness during the Antarctic winter
• high ultraviolet radiation during the summer
• large variations in nutrient supply
• Many Antarctic cyanobacteria produce antifreeze compounds and UV screens and are able to grow with very limited nutrients.

Cyanobacteria colonise Antarctic freshwater sediments, and  biofilms are formed when cyanobacteria  grow to such a high number that they form a continuous layer on top of a substrate. As they are filamentous - hair-like - they form a web or three-dimensional matrix.

They stay attached to the substrate by producing sticky substances. These so-called exopolymeric substances also enhance the matrix-structures.

Once the matrix structure is formed, other bacteria and microbial eukaryotes colonise the cyanobacterial biofilms and it becomes a microbial mat.

Microbial mats are characterised by a vertical stratification of different microorganisms. The chemical and physical gradients along the mat matrix are a result of the different metabolic activities of the inhabiting organisms and surrounding environmental conditions.

Cyanobacterial mat community

Cyanbacterial mat community in a meltwater pond on the McMurdo Ice Shelf, Antarctica

Cyanobacteria isolated from a meltwater pond on the McMurdo Ice Shelf, Antarctica