Scientist at Work Blog: Getting to the Bottom of It All

Michael Becker, a doctoral student at McGill University, was a scientific diver on an expedition to Lake Untersee in Antarctica.

If you?re going where there?s no air to breathe, you better be organized.

Any kind of underwater diving involves process for that very reason. There?s the early-morning wake-up, the weather check, the gear check (masks, fins, regulators ? check). And then there?s the dive site approach ? whether you?re walking in from the shore or taking a boat to some far forgotten reef.

Diving Lake Untersee is just like that ? except in Antarctica we get to our dive site by snowmobile. ?And Untersee ratchets up the workload because it?s remote, technical and cold.

To even get into the lake is a feat of accomplishment and a trick of clever engineering. Just the thought of trying to chip a dive hole through 10-foot thick lake ice could give you tendinitis long before you get your feet wet.

During the early days of Antarctic diving in the late-1970s, the expedition leader Dale Andersen and a few clever people working in the Dry Valley region of Antarctica came up with an ingenious way of getting through the ice. They modified an industrial-strength steam cleaner to circulate boiling hot liquid through a closed-circuit piece of copper tubing. All a would-be diver had to do was place the tubing inside a small hole drilled in the ice and wait for magic to happen as the hole slowly formed over two days.

But even when the hole is melted there?s still a lot to do before getting into the water.

Dive Days

We start with a hearty breakfast of dehydrated granola ? a meal that I hope to never see again. After breakfast, the diver gets ready by sorting the gear and putting on the dry suit while the first tender drives out by snowmobile to chip out any refrozen ice from the dive hole.

The second snowmobile carries the other dive tender and the diver (already in their dry suit) to the hole. The diver sits on the ice platform and is dressed with weights, tank, gloves, and is tied in to the all-important safety line.

This line is the life tether. It is fed out and taken in as needed. That way the surface assistants have a sense of how far away the diver is, and the diver knows where to return. In the early days, sequences of line pulls would be used to communicate simple commands like an early Morse code for dive messages. Nowadays, the dive line connects a surface communication box to the diver?s facemask. Diver and tender are easily able to grumble back and forth to each other with all the benefits of modern technology.

Once the diver?s mask is on they slide in, do the dive, come back to the hole and are yanked out. If the diver still has a pulse there is applause all around and we go back to celebrate with a dinner of dehydrated food.

Safety is paramount here and there is no margin of error. The nearest recompression chamber for a dive injury is 2,000 miles away in Cape Town. There are no helicopters for rescue and any serious injury or accident could mean death.

We follow all this protocol and process in pursuit of one thing ? studying microbial communities locked away from human history.

The Science Down There

Dale and I have done a number of dives to collect data and samples on the conical stromatolites found at the bottom of Lake Untersee. ?Dale has surfaced several times with sediment cores of the lake?s bottom. These cores tell us about the history of the lake and its resident organisms. By looking at cross-sections of the cores, we can see that the microbial communities grow over the years in layers known as laminations. These laminae show us a chronosequence of events, alternating between mineral deposition and organic layer growth. These mineral deposits must come from somewhere as the lake surface is covered in ice. It?s thought that the occasional influx of silt from nearby glaciers provides the sediment that the cyanobacteria then recolonize.

But there?s more than just grabbing a sample and returning to the surface ? the lake environment needs to be described in precise detail.

These cyanobacteria are photosynthetic and dependent on light to create their energy. One of my dives was spent swimming transects back and forth directly underneath the 10-foot ice ceiling holding a light meter. This gives us an idea of the amount of energy that is available for photosynthesis beneath the lake. The ice cover isn?t completely uniform; there are dark areas intermingled with sections of bright windows. Also, since light drops off with depth, not all life within the lake is receiving the same amount of energy.

It?s not just these cyanobacterial mats that thrive in Lake Untersee.

There is a diverse world of bacteria and viruses that inhabit their own unique sections of the water column all the way from the lake surface to over 500 feet below. These areas are far beyond our range capacity as scientific divers, and so we must rely on a different technique to sample these distant creatures.

Our two Russian scientists, Vladimir Akimov?and?Valery Galchenko from the Winogradsky Institute of Microbiology,?are microbiologists that specialize in microbial life in extreme environments. Their work has taken them from remote regions of Yakutia, Russia, studying heat-loving extremophiles, to the even more remote Lake Untersee to study the isolated bacteria inhabiting this lake.

Different communities of bacteria thrive according to the changing abiotic conditions, as you get deeper in the lake?s water column. ?These environments are mapped out by lowering sensors to measure conductivity, temperature, and depth, or CTD, from the lake?s surface down to around 330 feet ? our maximum sample depth.

Vladimir and Valery then lower their sampler to different points within the water column and capture about a gallon of water. These samples are brought back to camp, and the two spend hour after waking hour filtering the water to concentrate samples of both bacteria and viruses. There?s no human health concern with these viruses ? they are specific to the bacteria in the lake, and must exist in some sort of equilibrium with the lake life.

One of the areas that Vladimir and Valery are particularly interested is a section of the lake at 256 feet. At this depth, the lake chemistry changes quite a bit ? it becomes anoxic, meaning without oxygen. The organisms that thrive in this section have no need for oxygen in their metabolic processes. They use sulfur instead.

From a practical perspective, that means the samples reek. Rich in hydrogen sulfide, they smell like sour, rotten eggs. But by studying this transition from the clear, oxygen-rich water above to the dark, oxygen-poor water below we can get a sense of the two different worlds experienced by bacteria within the same lake.

What we bring up from the depths of Lake Untersee is only the beginning of a long scientific process. All these samples must be carried back to the civilized world, processed and analyzed over the next several months. Only then we will be able to more fully understand the ecosystem of Lake Untersee, and only then will we fully understand the significance of what we?re seeing.

And that?s what makes all this time, effort, and risk worth it. Diving Untersee has been an incredible experience, but without the questions driving us forward, it would be a lot to gamble for a good view.

Follow Michael on Twitter: @Michael__Becker or on his blog, ?The Dry Valleys.?

Source: http://scientistatwork.blogs.nytimes.com/2013/02/26/getting-to-the-bottom-of-it-all/?partner=rss&emc=rss

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