Diving into Lake Vanda's pale blue light
Working in an other-worldly environment brings challenges, writes DEIDRE MUSSEN .
Diving under the frozen surface of a lake in the middle of Antarctica's dry valleys is like "flying through a cathedral".
That is according to Tyler Mackey, a PhD student from the University of California.
He has spent December studying Lake Vanda's microbial communities for an international project, led by Canterbury University scientists and supported by Antarctica New Zealand.
His unusual subject means he has needed to master the rare skill of diving under ice-covered lakes to gather samples of bacteria.
On diving days, he and a fellow scientist don warm gear under a dry suit and a 90-metre tether for safety before slipping under the 3m to 4m-thick ice via a dive hole, which a heater keeps open.
Swimming below ice is far from terrifying, Mr Mackey says.
"When we're diving down there through the clear water with this glassy ceiling above us, it really is like flying through a cathedral because you're weightless and in your dry suit, just floating through crystal clear water with diffuse light coming in from everywhere. This sort of pale blue light sort of permeates everything."
However, the challenging environment requires concentration and a degree of seriousness.
"It's not done lightheartedly but at the same time, it's an environment where we have taken precautions for the setting and I think by being very intentional about what we're doing, we minimise the risks there while really getting some fantastic opportunities to do research, asking questions we wouldn't be able to ask just from the surface of the lake."
The lake is about 77m deep but Mr Mackey's dives are limited to about 28m so the lake's shallower edges are the main target for collecting samples.
There are no animals or plants in the water, unlike lakes elsewhere in the world.
Instead, the floor is covered with a thick carpet of bacteria, which is completely undisturbed.
During dives, samples of the carpet are carefully cut out using a spatula "like a piece of lasagne" and put into a container or a tube.
Mr Mackey's research examines climate impact on the bacteria, which grow a few millimetres annually and depend on light levels penetrating the water.
New Zealand has been involved with studies in the area since about 1970, when monitoring began on the Onx River, which flows into Lake Vanda and is Antarctica's longest river.
Since the 1960s, the lake's level has risen more than 10m due to climate change and that affects the amount of light reaching its bed.
The river is having more frequent high-flow years and the Lower Wright Glacier, which also feeds the lake, is generating more melt water as Antarctic temperatures rise. The lake has no outlet.
During their month-long stint in Antarctica, Mr Mackey and the team sleep in one-person mountain tents pitched near some huts at one end of the lake. The huts have facilities for cooking and lab space.
By day, they spend their time on the lake's glassy surface, and have to wear boot chains to stay upright as they go about their work.
Antarctica's dry valleys are the coldest and driest desert on Earth and frequently described as the planet's most similar environment to Mars.
"When you look around at the landscape here, you don't really see any life. It's rocks and sky and that's pretty much it but once you go below the ice, it's just life everywhere and so you really are entering into a different vision of the dry valleys of Antarctica, where it's brimming with life."
The underwater temperature is a relatively balmy 4 degrees Celsius compared with the colder, windier surface.
"So I think when we're diving in there, we feel sort of like we're getting the better end of the deal than the folks on the surface who are tending our line," Mr Mackey says.
However, dive gloves are relatively thin to allow good dexterity, which means cold fingers by the end of an hour- long dive.
He admits it takes a bit to get used to under-ice diving, such as remembering shallow water is lighter and darker water is deeper.
"When you're in that environment, it can actually be a bit disorienting because you've light coming from different directions and you don't really have a good cue for which way is up necessarily."
Mr Mackey is deeply passionate about his climate change studies and his work environment. While the lake's bacteria forest is not a typical "charismatic rainforest", he says it is as diverse and interesting.
"You're really swimming through the forest of these bacteria.
"It just happens to be on a much smaller scale than we think of ecosystems that we see around us. It's also a much more temperate environment.
"It's a very other-worldly experience and rather transcendent just being in a system so far outside of yourself and so apart from daily experience."