Century-old polar samples yield new insights

Scientists have analysed century-old specimens collected during the Discovery Expedition to Antarctica led by famed polar explorer Robert Falcon Scott (pictured). Photo / File

Century-old specimens collected by Captain Robert Falcon Scott's famed Discovery Expedition has yielded new insights into the state of Antarctica's pristine environment.

A new study by Kiwi and UK scientists, just published in the journal Proceedings of the Royal Society B, made a comparison between a form of specialist bacteria recently taken from Antarctica and samples collected by Scott's pioneering 1901-1904 Discovery Expedition.

The researchers were surprised to find little change over the century between - but say that shouldn't suggest climate change and other affects aren't posing an alarming threat to the continent.

Study co-author Professor Ian Hawes, of the University of Waikato, said the idea from the study materialised from an exhibition about the landmark expedition by the UK's Natural History Museum, where the samples had been preserved.

A friend and colleague of Hawes', Dr Anne Jungblut, had recently started at the museum and the pair saw an ideal opportunity to find out how quickly microbial communities "turn over" - or arrive and depart - in polar regions, something that could help gauge sensitivity of these microbial communities to change.

"If things are turning over all of the time, it gives them a lot of opportunity to respond to environmental change," Hawes said.

"When we started the project, we thought that we would see change over such a long time, since we know that the habitats these organisms grow in vary a lot with year-to-year differences in climate.

"Above all, we wanted to see if new organisms had been introduced from outside Antarctica. We hoped not, but expected that we would."

The introduction of new organisms to the continent was one of the biggest fears for what remains one of the last pristine, intact ecosystems on the planet.

The study was thought to be the first time the historic samples had been re-analysed - something performed using modern DNA extraction techniques.

Hawes said Antarctica's early explorers collected many specimens, and recognised that the dominant form of vegetation on land were cyanobacterial mats.

At that time, cyanobacteria were classed among algae, and the explorers preserved the specimens as they did seaweeds by pressing them between sheets of paper.

Samples returned to the UK were examined by some of the leading taxonomic figures of the time, before being put in storage until Jungblut pulled them back out.

Antarctica is home to one of the last intact ecosystems on the planet. Photo / Alan Gibson

The researchers faced two big hurdles: extracting usable DNA and ensuring the site the samples were taken from matched up with the modern comparison.

"Fortunately, the documentation of the samples was good, and the many accounts of the expeditions allowed us to be pretty sure that we were able to pin down the right places."

When Antarctica New Zealand agreed to a plan to take new samples, the team were able to analyse the two sets in different labs, but using the same method.

Hawes was surprised to see no dramatic change between the two.

"We often hear and talk about the fragility of Antarctic communities, and yet here we were looking at populations of bacteria that were hardly different after 100 years of growth, under variable conditions."

But there some indicators of change, including signs the communities had been slowly pushed in one direction by a changing climate.

And he said the overall finding was nonetheless significant in many ways.

It suggested organisms may be less delicate in the face of climate change than first thought, and that, although natural change came slowly, speeding the picture up meant serious trouble.

"We think that the underlying mechanism there is that the Antarctic winter places such a stress on inland organisms, and they are already so well adapted and acclimated to it, and grow so slowly, that it may be difficult for changes in natural populations to occur.

"There is a ecological inertia here and our fears for these unique assemblages are a little allayed.

"However, when we compare the speed with which communities are changing with the speed that the environment changes then it is a different story."

Hawes has also been involved in a project looking at how an increased melting of ice in the McMurdo Dry Valleys, not far from where the samples were collected, was affecting habitats of micro-organisms.

"We are finding that over the last 100 years, an increase in ice melt has led to a substantial increase in stream flow and rise in the level of many lakes.

"Nearby, other inland water bodies are drying up along with the cyanobacteria that they contain."

Hawes and his colleagues believe this change is due to a shift in wind pattern around Antarctica, with an increase in the frequency of warm winds in the Dry Valleys region.

"Coupling this with our findings from the Scott samples, we have a new paradigm for inland Antarctica, where we think that the habitats are more susceptible to change than the organisms in them.

"This is quite different to the ocean, where there are real concerns that small shifts in temperature and pH can cascade to big effects in genuinely sensitive organisms."