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.

Mummified seals can be found all over the Dry Valleys. It is believed that the seals came from the seas ice into the Dry Valleys . It is not known why exactly seals end up far away from the sea ice. Explanations could be that they become disorentiated due to sickness or bad weather conditions, and  starve to death.

Due to dry air and slow degradation processes in Antarctica the seal carcasses mummify and are thought to be hundreds of years old.

                                             Mummified seal near Canada glacier and Lake Fryxcell

                                                             Mummified seal near Koettlitz glacier

Although I have been writing already for several weeks about different regions and lakes in Antarctica, I have never posted a map.

                                                                                                         Antarctica

Map of Antarctica showing the location of Ross Island with US (McMurdo ) and the NZ Antarctic (Scott Base) stations, and the Dr Valley located in Victoria Land, continental Antarctica.

                                                                                     Dry Valleys (Southern Victoria Land)

Map of the Dry Valleys (McMurdo Dry Valleys ASMA Manual) , showing Pearse Valley with Lake Joyce, Wright Valley with Lake Vanda and Taylor Valley with Lake Hoare, which will be the last lake that we are planning to visit. The Dry Valleys are on continental Antarctica.

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.