Soils 101

January 19, 2010 by susanrwhitehead 2 Comments

One of the main areas of scientific research in the McMurdo Dry Valleys focuses on soils.  Many people are surprised to find out that there are actually soils in Antarctica, since we generally think of the entire continent as being covered by ice.  And that is true for about 98% of the continent.  However the dry valleys are a huge area (about 4,800 sq. km) of exposed rock and soil. The first explorers here gave a pretty bleak description of the area:

“We have seen no living thing, not even a moss or lichen.”

-Robert F. Scott, 1903

At first glance the dry valley soils look completely barren. All of the life here is microscopic.

However, scientists today will tell you otherwise.  It turns out that the soils in the dry valleys are occupied by some fascinating critters, which can only be seen with the aid of a microscope.  Trying to understand the distribution, abundance, and activity of these tiny invertebrates is the primary goal of the team of scientists known here as “wormherders”.

There are two scientists that head up the wormherder team in the McMurdo Dry Valleys.  One is Dr. Diana Wall, a professor at Colorado State University, and the other is Dr. Ross Virginia, a professor at Dartmouth College.  They have both been working here in Antarctica for many years, and, with the help of their post-docs and graduate students, have learned a lot about the soils in the dry valleys.  Each year they come to maintain their long-term experiments, measure various chemical properties of the soil, and collect samples they can use to examine soil invertebrates.

Bishwo (a graduate student at BYU), Dr. Wall, and Dr. Byron Adams (an LTER collaborator and professor at BYU) collect soil samples from one of their long-term soil plots near F6

Dr. Wall and Dr. Virginia have found that about 65% of the soils they sample in the dry valleys contain life.  They generally see up to three types of invertebrate animals—nematodes, tardigrades, and rotifers.  This is probably the simplest soil ecosystem in the world.  The top of the food chain is a nematode, which is a predator, and most other invertebrates are microbial grazers—so they eat even smaller microscopic organisms such as algae or bacteria.  The wettest soils, such as those near streams, contain the most species, whereas the drier soils contain only one species of nematode—Scottenema lindsayae.

The soils here are not an easy place to live—they are the oldest, coldest, and driest on earth.  The dry valleys are considered a polar desert.  It rarely snows, and when snow does fall, it disappears VERY quickly.  Most of the snow sublimates, which is when frozen water is transformed directly into water vapor, without ever actually passing through the liquid stage.  We were lucky to be in the dry valleys for one of these rare snow events—we woke up one morning to a beautiful dusting all over our tents.

Snow in the Dry Valleys!!

But all this snow was GONE about an hour later.  It was incredible how quickly it disappeared.  In order to survive these extremely dry conditions, the soil invertebrates enter into a state called anhydrobiosis.   Anhydrobiosis is sort of like an extreme version of hibernation.  All of the normal metabolic processes, such as cellular division, repair, and reproduction, completely stop.  Most of the water inside the cells of an anhydrobiotic organism is lost or replaced by a sugar solution, which is less likely to freeze, and generally the body contracts into a smaller shape.  Once in anhydrobiosis, nematodes and tardigrades can survive for many years until water is available again, and are virtually indestructible.  You can freeze them, boil them, soak them in ethanol, or submit them to radiation, and they still won’t die!  Some people call them the toughest organisms on earth.

SEM of a tardigrade (Source: http://knol.google.com/k/tardigrades#)

SEM of a tardigrade in anhydrobiosis (Source: http://knol.google.com/k/tardigrades#)

We were lucky to be here at F6, our field camp, when the soil researchers came to work on their research plots.  They had a lot of work to do maintaining some of their experiments—in particular the stoichiometry experiments where they are looking at the effects of carbon, nitrogen, and phosphorus additions on soil biota.  One day they arrived with 35 giant 10-liter jugs containing pre-mixed nutrient solutions, which had to be carefully added to their experimental plots.  When we weren’t working, we enjoyed chatting with the soil researchers over hot tea or coffee in the F6 hut.  Getting to meet other scientists and talk informally about research is one of the best parts of being here in Antarctica—everyone has an interesting story to tell!  You can read more about the wormherders and their work in Antarctica on their blog.