Captain Scott's legacy supports Antarctic biodiversity research
21 June 2017
Bacterial samples collected by Captain Scott's Discovery Expedition more than 100 years ago have been used to assess the current state of Antarctic biodiversity.
Scientists have compared the historic samples, which are cared for in the Museum, with modern ones taken from the same areas.
The research reveals that the populations of these specialist bacteria, called cyanobacteria, have changed little over the past 100 years.
'One of the reasons we think the cyanobacteria community is so resilient to change is because it is adapted to environmental stress and surviving long, freezing Antarctic winters,' she says. 'If a warming climate means fewer days of freezing, then their habitat may be destabilised.'
An ecosystem under threat
Life in the Antarctic is a struggle against the coldest and driest conditions in the world, with months of winter darkness and high ultraviolet light exposure in the summer. Life forms on mainland Antarctica therefore tend to be simple and hardy, like bacteria, lichens and some small invertebrates.
Researchers are worried that climate change could affect these unique biological communities. While the main continental landmass of Antarctica has warmed much less than the Arctic, scientists expect the warming to accelerate.
To monitor the ecosystem effectively, scientists need a good understanding of not only which organisms are currently present, but whether their populations have changed over time.
'The outcomes of our study highlight the ongoing legacy of Captain Scott’s expeditions for Antarctic sciences,' says Dr Jungblut.
'These historic samples were taken in 1902-1903, before regular human activity on the continent. They have allowed us to create a baseline against which to carry out future monitoring of the freshwater biology of inland Antarctica. This will help us to better assess the effect of any climate-driven environmental change.'
Watch a flyover of freshwater ponds on the McMurdo Ice Shelf. Despite the harsh conditions, they are home to a unique ecosystem.
Cyanobacteria as food and habitat
Cyanobacteria (also known as blue-green algae) are keystone organisms in Antarctic freshwater lakes, playing a crucial role in their ecosystems. As they are photosynthetic, they make their own food from sunlight and in turn serve as a source of food for other organisms.
The hair-like cyanobacteria can also grow and knit together, forming a structure that other microorganisms then live on. These complex mini-ecosystems are called microbial mats.
The video below shows cyanobacterial communities living underwater in microbial mats on the McMurdo Ice Shelf:
A historic expedition
The historic, cyanobacteria-dominated microbial mat samples examined in the new research were collected on the first expedition that Captain Scott led to the Antarctic, from 1901 to 1904. Commonly known as the Discovery Expedition, after the name of its ship, its aim was to carry out both scientific research and geographical exploration.
Members of the mission would go on to further polar adventures, including the explorer Ernest Shackleton and the physician, scientist and artist Edward Wilson. Captain Scott himself famously perished on a later expedition to the South Pole.
The Discovery microbial mat samples were collected and prepared by Dr Reginald Koettlitz - senior surgeon, bacteriologist and botanist on the expedition - and Dr Edward Wilson, who acted as his assistant. The samples were collected from the edges of thawing shallow freshwater ponds on Ross Island and the McMurdo Ice Shelf.
Dr Jungblut and collaborator Prof Ian Hawes of the University of Waikato, New Zealand, compared the populations of cyanobacteria in the historic samples to modern ones taken from the same areas to see if there had been any notable changes in the species present.
As there can be hundreds of species of bacteria in one sample, the scientists identified them by signature parts of their DNA.
Ross Island is currently experiencing one of the highest levels of human activity in Antarctica. It is particularly at risk of the introduction of alien and potentially invasive species.
However, the team found that the general populations of cyanobacteria in the microbial mats have changed little over the past hundred years. According to Dr Jungblut, this may be because Antarctica is challenging for new species to get a foothold in.
'It may be that the high stress environment has selected over time a population of organisms that tolerate conditions such as winter freezing; short, cold summers; salinity and variation in nutrients.
'We think that existing communities are likely to be resistant to a moderate degree of climate change, as long as the overwhelming stress of winter freezing and a short summer growth period continues.'
No cause for complacency
While the current microbial ecosystem looks naturally resistant to invasion, Dr Jungblut warns against complacency, as both climate change and human activity in the area could introduce new species in future.
'The risk of other, more invasive wildlife such as insects reaching Antarctica remains - as does the possibility that synergy between climate change and human activity may allow these new species to colonise these ponds and disrupt microbial biodiversity and ecology.
'It is essential that the current biosecurity protocols - designed to limit the introduction of non-native biological material through human activities - remain for Antarctica.'
- By James McNish