Saturday, January 31, 2009

How to Walk in the Dry Valleys

The dry valleys are a very sensitive ecosystem. Because it's such a harsh place for organisms to live, they do not grow very fast. We don't want to make it any harder for them! Plus, we want the ecosystem to stay as clean and healthy as possible, without creating too much of a disturbance ourselves. We want to avoid damaging the ecosystem and the organisms as much as possible. Therefore have to be very careful when we work in the dry valleys.

The main way we can disturb the environment is by walking. We have to walk a lot to get to our camp and field sites for work. There are very specific ways we walk here to minimize the amount of disturbance we create with our feet.

When we're walking on the ground to and from our field sites, we always walk single-file so that only one line of footprints is made. We follow paths made by the polygon cracks in the ground. These cracks are made by the repeated freezing and thawing of the ground, and they form a variety of interesting shapes, called polygons. When you look at the ground from a helicopter, you see all of the polygons that make up the dry valley landscape.
Our previous research has shown us that soil biodiversity is lowest in these cracks. There are fewer animals living in the soil at the cracks than in the flat part of the ground. So, we try to always walk in the cracks. That way, our footsteps are trampling the least amount of organisms as possible. It unfortunately means that we can't walk in a straight line anywhere! You have to follow the zig-zagging of the polygon cracks to get from one place to another, which means sometimes you walk twice as much as the distance you need to go! Here's what it looks like as you walk in the polygon cracks:
video

When we're working at our field sites, we try our best to not trample the soil too much. We stand on rocks as much as possible. If we want to sit down, we sit on rocks, like Katie is doing:

Sometimes we work near streams, especially for our moss research. We don't want to disturb the algae and moss growing in the sediment in the streams. To avoid trampling anything, we rock hop. Every step we take has to be on a rock, where algae are not growing. This is pretty easy when the stream flow is low and the rocks are exposed, but it can get tricky if the water is high!
video

Sometimes we even have to rock hop to walk across the dry ground. The polygon cracks cover most of the soil, but they're not everywhere. When there are no cracks, we rockhop across the ground so that we don't disturb the soil!

Most of the places we walk are on soil and near streams. But, sometimes we walk on the ice. We don't have to be as careful about the ecosystem when we're on the ice, because there's not much damage we can do. But, we still have to be careful! The ice is slippery, of course, so we wear stabilizers attached to our shoes that give us better traction. Also, the glaciers and lake ice are covered with cryoconite holes. These holes are formed when dirt or rocks are blown onto the ice. Because the rocks are dark, they absorb more of the sun's heat and melt the ice around them. The rocks sink down as the ice melts, leaving a lot of little holes in the ice. These holes might be several inches deep, or even deeper! They can be just a couple inches wide, or they can be much bigger! It depends on the size of the rock that landed there to melt the ice. Sometimes the holes are filled with water. We have to be careful not to step in them, because if you do, you'll suddenly find yourself standing in a deep, wet hole! Sometimes the cryoconite holes have been covered back over with a layer of ice on top that maes the holes hard to see. But, that layer of ice is not strong enough to hold a person, so you crash through unexpectedly. You have to keep an eye on the ground so that you know you're stepping on thick ice. This is what it looks like to walk over the top of a glacier in the dry valleys. This is from our Christmas Eve hike over the Canada Glacier:
video

We do a lot of walking while we're here. Now you know what it's like!

Friday, January 30, 2009

Camp Hair Contest Winner

The week has passed, and the votes have been tallied. The winner of the 2008-09 Best Camp Hair Contest is...

BREANA!!

This proud wormherder celebrates her victory by sporting her favorite facial hair accessory- a mustache! It's a very expensive mustache to have grown.Congratulations Breana!

Sunday, January 25, 2009

Old Antarctic Explorers

Antarctica has a long history of exploration. Explorers, mainly from Europe, were frequently coming to Antarctica during the late 1800's and early 1900's during what is called the "Heroic Age of Exploration". The goals of the explorations were mainly scientific. They wanted to study the geography of Antarctica and reach the South Pole. This was a very difficult time to be an Old Antarctic Explorer. Resources were scarce down here, working conditions were strenuous, and of course the weather was harsh! Explorations tended to be a feat of endurance, both physically and mentally. A lot of people died during expeditions to explore Antarctica and reach the South Pole.

One particular OAE that is important in the McMurdo area is Robert F. Scott. He led several missions to this area of Antarctica. After exploring a lot of this region, Scott led a party in an attempt to reach the South Pole. He was racing the Norwegian explorer, Amundsen, to be the first to reach the South Pole. Unfortunately, the trip did not go well for Scott. They did reach the South Pole, but they were beaten there by Amundsen's party. And, on the journey back to the coast (here at McMurdo), everyone in Scott's party died due to the harsh conditions. Surprisingly, they were only 11 miles away from a supply hut when they died. It is a very unfortunate story!
A statue of Scott is in Christchurch, NZ. We always visit it on our way down to the ice. Here's Katie with the statue, back in December when we were passing through.

A lot still remains of the early explorations. Near McMurdo, there is a hut that was built in 1902 by Scott during his first mission, called the Discovery Mission. The hut is called (cleverly) Discovery Hut, and sits on Hut Point just outside of McMurdo. Several huts like this were built around Antarctica to be supply stations for explorers along various points on their journey. It is Discovery Hut that Scott's South Pole party was trying to reach when they died.Because Antarctica is so cold and dry, these huts are very well preserved. The food and equipment that explorers used are still in the huts. We were lucky enough this year to be able to go inside Discovery Hut and see what's in there! Here's a video I took walking through the hut. You can hear Breana telling some facts about the hut and Katie asking questions. It's neat to see all of the old supplies, like what kind of food they eat and clothes they wore!

video
Some of the facts Breana is reading:
These huts were built in Australia, fashioned after Aboriginal huts that were designed to keep cool during the hot summers. Scott thought that it would work the same for keeping warm in cold Antarctica. But, he was wrong! The building was not warm enough for people to live in, so it was used for storage and cooking. Instead, the people lived on the boat just offshore. They heated the building with a blubber stove. That's the brick structure in the floor towards the end of the video. You can sort of see the huge chunk of freeze-dried whale blubber behind Uffe at the beginning of the tour (it's in a shadow, so hard to notice).

It was pretty neat to be able to see this little piece of Antarctic history. It's amazing to think about the conditions that the early explorers had to deal with. They're the same type of conditions we deal with here, but we're much better equipped now!

Winding Down

Our field season at McMurdo is starting to wind down. Ross is leaving today to head back to the U.S. Katie, Elizabeth and I are here just one more week to finish up our work. We are scheduled to head back to New Zealand on February 2.

We have just two more days of field work left for this coming week. Other than that, we are processing the last of our samples and breaking down the lab. We are cleaning out the lab, returning field gear, and gathering up our shipments to send home. All of the soil and moss samples we've collected over the season are getting boxed up to ship back to Dartmouth. We will have a lot more work to do with them once we return home.

It will be a busy week!

Thursday, January 22, 2009

The Dry Valley Forest

As I've said before, Antarctica is a very hard place to live. It's not just hard for animals, but also for plants. It's very dry, so plants cannot get much water to grow. The only time water is plentiful is during the 14 weeks of the year when the meltwater streams are flowing, and that water is only available if you're right next to the stream. Sunlight is also a problem. During the winter there's no sunlight for photosynthesis, but during the summer the sun can be so intense that it can actually damage plants. So, it takes a very hardy plant to be able to grow here!

The only plants we have in the dry valleys are mosses. Very short mosses. There are no vascular plants, which are what most people think of when they hear the word "plant". Mosses mainly grow in patches along streams or beneath snow patches, which is only a small percent of the land area. They grow incredibly slowly. We're talking less than a millimeter of growth per year! Most of the moss we see look like the photo above from right outside the Lake Fryxell camp hut. They're not lush and green, because they're usually too cold, too dry, or have too much sun damage. But, sometimes you find a nice, lush green patch like the one below! This patch was probably recently uncovered from water, so is still very happy.

One of the really cool things about this patch of moss that Elizabeth, Katie, and Ross found is that it has reproductive structures. Moss is able to reproduce in two ways. It can reproduce by itself, where bits of the moss break off and become a new moss plant. In the dry valleys, these small bits of moss might blow in the wind to a new location, so that moss spread to new areas. Moss can also reproduce with each other. For this, the moss grow special structures. These special structures act like male and female parts, so that the sperm from the male structures fertilizes the female structures, forming spores (which are sort of like seeds in plants). When they're ready, the spores are released from the female structures to seed new areas. (Click here to see a video of moss reproduction.)

It is generally thought that moss in the dry valleys spread by pieces breaking off and becoming new mosses, not by developing spores. Growing the special reproductive structures requires a lot of energy and resources that are very hard to come by in the dry valleys. But, in this happy patch of moss, we see reproductive structures! Those white-ish stems coming up are the structures that contain the spores. Here's what one looks like under the microscope:


Moss is the only above-ground life in the dry valleys. All of the other organisms live in the soil, not on it. So, moss are in a way like the redwood forests of the Antarctic Dry Valleys! They are one of the few sources of food for soil organisms. When mosses die, they decompose in the soil, just like plants in warmer climates. The carbon and nutrients released from mosses when they decompose are probably a very important part of the soil food web. That is why so much of our research this year focuses on mosses. We want to know more about their role in the carbon and nutrient cycles in the dry valleys. We measure their photosynthesis rates, so that we know how much carbon they are taking from the air and putting into the soil. We measure their nutrients, so we know what type of food they are providing to the soil organisms. We measure how they respond to changes in moisture and nutrients in the soil, so that we know how stable their role is in nutrient cycles.To see how the nutrients in moss respond to changing the nutrients around them, we spray salt solutions that contain nitrogen or phosphorus onto the mosses (very similar to the stoichiometry experiment using the "hula" cones). Here's a patch of mosses next to one of the streams. It's buried in silt a bit, but there are mosses down there! Katie is spraying the nutrient solutions on them. While we were at F6 this week, we took samples from the plot to see if adding nutrients around the mosses changed the nutrient content of the mosses themselves. We also have these plots set up around a few other streams that we will have to sample in the next week.

Tuesday, January 20, 2009

2nd Annual Camp Hair Contest

It is time for the Second Annual McMurdo Field Camp Hair Contest!

The water restrictions in the dry valleys means that we are not able to shower or wash our hair while we're out at field camps. That means that people's hair gets very dirty and oily, which of course leads to some very fabulous hair-do's! This is what we call having "camp hair." Having great camp hair is a matter of pride, and the person with the best camp hair is honored throughout McMurdo. So, once again, I'm going to leave it up to everyone reading my blog to decide who has the best camp hair for the 2008-09 field season. Review the photos below of our "camp hair" contestants, and send in your vote! Anyone reading this is welcome to vote, and can do so by sending an email with your choice to me.

Let's meet this year's contestants!

Elizabeth:Returning champion Elizabeth is once again demonstrating her all-natural, gravity-defying camp hairdo. While the front of her hair has been flattened by hours of lying under a hat, don't let that fool you! The back of her head is 4 inches taller than the rest of her! Photo taken after 5 days in the field.

Katie:Recent Dartmouth graduate Katie is featuring the Cindy Loo Who look. The dry air can't keep her hair down, oh no. This springy look comes after 5 days in the field under the influence of wind, sunblock, and home-made wool hats.

Corey:
With only 3 camp-showers over the course of his 40-day field stint, stream-team member Corey's hair has been dirtied, wind-blown and pelted by sand particles. Much like this ventifact. Coupling his hairdo with a savage beard, Corey presents a look that is hard for our other gals to match.

Breana:This wormherder postdoc's look just screams "Troll Doll". Breana does not need multiple days without a shower to master this fine look. On Day 1 in the field, this is her hair's reaction to a mere few hours of being trapped under a hat. When her hair is released from under her hat, watch out!

There they are: the 2008-09 season's Best Camp Hair contestants. May the voting begin! The champion Camp Hair will be declared a week from today.
After a full day of weather delays on Saturday (and our wonderful luau), we finally made it back out to F6 on Lake Fryxell. However, the bad weather took out our internet! We finally had IT guys come in today to fix it, so we've been reconnected with the outside world.

We've been busy with lots of field work for the past several days. But, it's been very cold! I'll catch you up on all of our work since we lost connection over the next few days. Right now, it's time for a hot drink and some dinner!

Friday, January 16, 2009

More Weather Delays

The weather has been very uncooperative for the past week and a half! It was hard getting everyone back into town after our field work last week, because the weather was bad and the helo's couldn't fly. Katie, Elizabeth, and Ross got stuck out at Lake Fryxell camp for an extra day because no helo could get into the Valley to pick them up. I kept trying to leave McMurdo to go to Lake Bonney, but that trip kept getting canceled. We finally made it to our destinations, after a couple days of delay. We all made it back to McMurdo on Tuesday, after completing most of the work we needed to do last week. Since then, we've all been back in McMurdo processing samples in the lab. Today, we are once again trying to get back to the field. We were all supposed to fly out this morning to F6 camp on Lake Fryxell. But, it's snowing again, and you can only see about 200 m across McMurdo Sound, so we're not going anywhere!

Since we're all stuck here in town, we decided to have a luau on the Florida Keys (after my walk to the post office to pick up some super fun packages that were sent to me). We decorated ourselves using my Luau in an Envelope kit. And we basked on the edge of the miniature beach that was sent to me from Florida (which I'm holding in my hands). Here we are partying in the hallway in the science building: Karen, Katie, Diana, Breana, Uffe, me, and Bishwo. Of course, we also decorate any passers-by, so now there's a lot of people in the science building in Antarctica that are dressed for a luau!There's still a small chance we could get out to F6 later today. But the weather is not looking so good, which means we may be stuck in town until Monday. I'll keep you posted!

Thursday, January 15, 2009

Nitrogen Fixation

Nitrogen is the most common element in the atmosphere and the air we breathe (78%), and it is a necessary element for life. It is an important element in proteins and enzymes, including the enzyme that allows plants to photosynthesize. However, the form of nitrogen that is in the air is not usable by plants. Plants use nitrogen compounds in the soil, not the nitrogen gas that is so abundant in the air. So how does all of that nitrogen from the air get into the soil for plants to use?

There are some organisms called cyanobacteria that can use the nitrogen gas in the air. They have special cells (called heterocysts) that can can grab nitrogen gas from the air and change it into a usable compound. This is a process called "nitrogen fixation". The cyanobacteria use that new form of nitrogen to grow. Then, when the cyanobacteria dies and decays, that usable form of nitrogen is released in the soil for plants and animals to use.

We see a lot of cyanobacteria near the streams and lakes in the dry valleys. It will grow in thick mats, like you see here. All of that black stuff is a bunch of cyanobacteria matted together, making a layer on top of the soil. One of the things we want to know is how much nitrogen the cyanobacteria are fixing. That way we can estimate how much nitrogen they are adding to the soil for the mosses and other soil animals to use. Unfortunately, it is not very easy to measure nitrogen fixation. But, we can measure a similar chemical process called "acetylene reduction" that helps us calculate how much nitrogen is being taken from the air. To measure acetylene reduction, we place small amounts of cyanobacteria (and mosses with cyanobacteria growing on it) into air-tight chambers, like the clear plastic ones in this picture. We then add a gas called acetylene to the chamber. The cyanobacteria will change the acetylene to ethylene in a process similar to how they change nitrogen gas. We leave the pieces of cyanobacteria and moss in the chambers for 1-5 hours. Then, we take a sample of the air inside the chamber and put it in a special vial. We then measure the amount of acetylene that has been changed to ethylene, and we can then calculate how much nitrogen would have been fixed from the air.

Here's Elizabeth and Ross measuring acetylene reduction at one of our field sites. Elizabeth is using a big syringe to pull new acetylene from a bag to inject into the plastic chambers. Ross is using another syringe to remove a gas sample from a chamber that contains some cyanobacteria.
We will take the vials of gas samples back to Dartmouth and measure the concentration of ethylene on one of the machines in our lab at home. So, we're doing the work now, but won't see the results for another month!

Sunday, January 11, 2009

Dry Valley Wildlife

Most people think of Antarctica as being a big, cold, dead place. When you see photos of our research in the dry valleys, you don't see animals. But, there are animals there, in every single one of those pictures! You just can't see them, because they're microscopic. Here's some information about the main types of micro-organisms that live in Antarctic soils.

Nematodes
Also called roundworms, nematodes live EVERYWHERE in the world. You can find them in every biome in the world. They live in water, soil, ice, even in other animals! They are the most abundant animal in the world. In the dry valleys, we find more nematodes than any other animal. They are what our collaborators at Colorado State focus on studying. We have three main species that live here. The most numerous species, Scottnema lindsayae, is in the photo to the left.

Nematodes eat a lot of different things. Some, like the guy at the left, eat bacteria. Others eat fungi or algae, and some are even predators that eat other microscopic soil organisms. In the dry valleys, a predatory nematode is the top of the food chain! Though nematodes are small, they have a lot of very well-defined characteristics. Here is a very close-up picture of the mouth-parts of a bacterial-feeding nematode. They use those long branches on their mouths to scrape bacteria off of soil surfaces.

Rotifers
Rotifers also live in a lot of different environments, including fresh water, saltwater, soils, and other watery environments. A rotifer eats by waving the hairs around its mouth (at the top, in this picture) to catch things floating in the water. The moving action around their mouth looks kind of like a wheel, which is how they got the name ROTifer (like rotate). The "foot" (at the bottom of the picture) is to anchor the rotifer when it doesn't want to move.

Tardigrades
Tardigrades are also called water bears, and looking at the picture I think you can see why! They even have claws at the end of their feet, which you can see in this very close-up microscrope picture that Uffe took of a tardigrade foot. The claws let them hold on to something as they float through water or the water-filled spaces in the soil. Tardigrades eat with a stylet that they use to pierce animal and plant cell walls.

Tardigrades are able to live in a lot of extreme environments, and are found everwhere from the Himalayas to the ocean floor to Antarctica. They can withstand the pressure of a vaccuum, radiation, dehydration, and both incredibly high and low temperatures. There are even experiments that test tardigrades' ability to live in open space! In the dry valleys, they especially like to live in the moss and algae patches, where food and water are readily available.

The soil environment in the dry valleys is a very hard place to be an animal. There's not a lot of water, not a lot to eat, and it is very cold! Most of these micro-organisms have a special ability to help survive in such a harsh environment. They can go into anhydrobiosis, which essentially means they can freeze-dry themselves. They can push out all of their water and curl up, so that they don't freeze and die. Their metabolism drops to almost a stand-still! They can stay in anhydrobiosis for a very long time, and immediately wake up if water becomes available.

Part of our research looks at what animals are living in the soil. We want to know why they live in some places in the dry valleys, but not others. We want to know how nutrient cycles in the soil change when animals are there or not. So, we spend a lot of time on the microscopes looking at the animals we can extract from the soil. One of our team members, Byron, made this awesome video through the 'scope featuring three of our soil superstars: nematodes, rotifers, and tardigrades.

video

[Photos of each are from the linked websites: S. lindsayae, rotifer, tardigrade. Video by Byron Adams. Tardigrade foot photo taken by Uffe Nielsen.]

Friday, January 9, 2009

Tracer Experiment

Well, we finally made it out to the field. The weather at McMurdo has been very patchy. There's been snow and a lot of clouds. But, the weather out in the Dry Valleys has been very nice. So, once they finally had a short window of time to get us out, we left McMurdo and have been staying in the Valleys ever since in some beautiful, sunny weather. Katie and Elizabeth made it out to Lake Fryxell on Wednesday afternoon. Ross and I made it out to Lake Bonney on Thursday afternoon.

At Lake Bonney, Ross and I were working on an experiment that traced the movement of water from melting permafrost flowing over the soil. Permafrost is soil and rock in the ground that stays permanently frozen year-round. It usually is found below the soil surface in cold places like Antarctica and the Arctic. During the summer in the dry valleys, the permafrost will melt a little bit, causing wet patches to appear in the soil. You can see those darker, wet patches of soil in this picture at Bonney:Because it's been so warm this year, the permafrost below the soil has been melting a lot more than usual. At one of our research sites at Bonney, that meltwater has reach the surface (kind of like a spring you might find in the mountains in the US). There's so much meltwater that it ended up forming a stream that flows all the way down to the lake, straight through some long-term sampling plots we set up years ago! (Our team nickname in McMurdo is the Wormherders. Because the stream flows through one of our plots, it is called Wormherder Creek.) Instead of being upset that our plots are ruined, we're using the opportunity to learn about sources of water in the dry valleys and how they influence the soil.

On Thursday, we soil ecologists teamed up with a group of stream ecologists to study how the new Wormherder Creek interacts with the soil to influence soil chemistry and organisms. We added chemicals containing lithium and bromide high up on Wormherder Creek, and we followed how those chemicals moved down the stream and through the soil. There were two people at the top of the creek at the chemical injection site running the pump. Then, there were scientists stationed at regular intervals down the stream collecting samples every 5 or 10 minutes. I was stationed higher up on the creek with Uffe. In this video, you see Uffe labeling the bottle to take the next sample. That bottle gets dipped into the stream flow to be filled with water. You can see another scientist, Anna, further down the stream at the next station. You can also see how fast that meltwater is moving! It's a small creek, but there's a good bit of water in it! The tube next to the orange flag is called a piezometer, which is how we extract ground water from below the surface.
video

We collected a lot of surface water, ground water, and soil samples for several hours through the night. We will look for the presence and concentration of the chemicals we released high up in the stream so that we can follow how the water moved down to the lake. We will also measure the chemistry of the water and soil, and look at what kinds of organisms we find in various locations, to see how those important properties are influenced by the presence of Wormherder Creek. It was a loooong night, but we finished it!

After we left Lake Bonney late Thursday night, Ross headed to Fryxell to be with Katie and Elizabeth. I have been back at F6 (across the lake from the rest of the group) working on the stoichiometry plots that we treated last week. Hopefully I will be heading back to Lake Bonney tomorrow, but the weather does not look good in McMurdo, so the helicopters may not be able to come get me! Keep your fingers crossed, because I have samples to get back to the lab!

Tuesday, January 6, 2009

My bags are packed, I'm ready to go....



Because the Dry Valleys are so remote, we fly on helicopters to get there. Today we were supposed to fly to Lake Fryxell and Lake Bonney. But the weather is very bad for flying right now so we can't go anywhere. Helicopters only fly when the sky is clear and the wind is not blowing too hard. The helicopters here at McMurdo have lots of jobs to do, such as taking people to different places, delivering packages to field camps, and moving large pieces of equipment. Even though the helicopters have many jobs to do, safety is more important than everything else. So if the weather is bad enough, they all stay on the ground. Usually from the helicopter pad you can look out at the Ross Sea and also see the mainland on the other side. As this picture shows, you can't see much of anything this morning.

Last night we got a few inches of snow in McMurdo, even though it's the middle of summer!

We come down to Antarctic with plans to do lots and lots of scientific research, the weather is unpredictable. Sometimes we simply can't get out to our field locations and must wait for the weather to clear. So that's what we're doing today... waiting for better weather!

Monday, January 5, 2009

In and Back Out Again

Our final team member, Ross, arrived Saturday night. So, we are now a complete group of 4 from Dartmouth! Together, we've spent the past couple of days in McMurdo in our lab processing our samples.

Katie is working on a procedure called Chloroform Fumigation Extraction. For that, she is measuring the amount of carbon in the soil that is released after adding chloroform. Chloroform is a chemical that breaks open cells of living organisms (including people). So, if the carbon is released by the chloroform, it was released by the microbes living in the soil. Measuring the amount of carbon released by chloroform gives us an estimate of the microbial biomass living in the soil we are studying. Of course, Katie has to be careful not to breathe the chloroform herself. (Don't worry: when this picture was taken, she was already finished with the chloroform step!)
Elizabeth is busy picking all of the rocks out of her soil samples. The soils she is studying are very rocky, and the pebbles have to be removed before she can measure their chemistry. Doesn't that look like fun?!

We will be heading out to the field again tomorrow. We will be splitting up into two groups so that we can get more work done. Katie and Elizabeth will be going back to Lake Fryxell where we went the first week of our field work. Ross and I will be moving around all over the valley for the rest of the week. We'll be busy!

~~~~~~~~~~~~On another note~~~~~~~~~~~~~
Check out the awesome card I got in the mail yesterday, drawn by my friend Bob! Cedar waxwings like these live in the trees outside my office back at Dartmouth, so I put the card over my desk here in McMurdo to remind me of home.

Sunday, January 4, 2009

Now where was that?

The plants and animals that live in the Dry Valleys are very small. Because they are so small, they are often difficult to locate, and even more difficult to find a second time.

This picture shows how closely you have to look to find the mosses that we study.

There are also no road signs pointing us in the direction of our research sites. We study certain spots in the field during one research season and try to get back to those same locations the next year. This is challenging because there are very few land features that we can use to remember a certain location and some things change from year to year. The streams are fed by melted snow, so they change depending upon how much snow falls during the winter and melts in the summer. This stream might have looked completely different last year, so finding a particular bend in the stream is nearly impossible.

Because of these navigational challenges, we use a GPS to help us find places in the Dry Valleys.
GPS stands for Global Positioning System. It uses satellites orbiting the earth that transmit signals, which enable GPS receivers to determine their current location. A GPS tells you your location in latitude and longitude coordinates. When we want to be able to find a certain spot again, we record the latitude and longitude coordinates so that we can later return to that exact location using the GPS.

Here's a picture of Elizabeth using a GPS to record the coordinates of a study site. If she wants to come back later, all she has to do is tell the GPS to find those coordinates and it will point an arrow in the direction we need to walk to get there. It also tells you distance.

A GPS isn't perfect. Sometimes we have a really hard time finding a spot using the coordinates a GPS gives us. It is often about 10 meters off, which is a lot when your study subject is only 1 centimeter tall. But the GPS is a very useful tool and we are very happy that it's in our scientific toolbox!

Friday, January 2, 2009

Stoichiometry

This morning, Katie and I flew to the Lake Bonney basin for another two days of field work.
While we are here, we will be working on a project that will tell us how the soil and soil organisms respond to nutrients added to the soil.

There are three main elements that are very important for life everywhere: carbon, nitrogen, and phosphorus. These nutrients are important for all organisms to grow and live. If one of these elements is in short supply, organisms cannot continue to grow. So, the amount of nutrients in the soil can be limiting to life. We want to know which of these elements are limiting to life in the dry valleys.

We have set up areas where we add carbon, nitrogen, and phosphorus to the soil. Each year, we add more of the nutrients and measure how the microbes and invertebrates living in the soil respond to the additions. We add the nutrients by dissolving sugar and salt in water, then pouring the water over the plots. Some plots get sugar water (for carbon), some get water with nitrogen or phosphorus salt added, and some get both sugar and salt. In this photo, Breana is adding some nutrient water to one of the plots.

We use the plastic cone to prevent the wind from blowing the water away before it reaches the ground. Or, you can be like Uffe and wear the cones as a hula skirt:
After we add the nutrients, we measure respiration to see how active the microbes are. We also measure the amount of nematodes in the soil and how the soil chemistry changes after the nutrients are added.

We've been working on this project for many years. So far, we have learned that carbon is most limiting to life in the dry valleys. Carbon in the soil mostly comes from photosynthesis by plants. Plants are able to take carbon from the air (as carbon dioxide) and turn it into forms usable by soil organisms. Because Antarctica is so cold and dry, there are not a lot of plants. We only have some mosses and algae that can photosynthesize, and they are only found near sources of water. Because there's not a lot of photosynthesis, there is not a lot of carbon added naturally to the soil. So, carbon is often the limiting nutrient in the dry valley soils, which is why we notice the biggest response in the activity of the organisms when we add carbon.

Nitrogen and phosphorus may also become limiting in the soil, if there is enough carbon for organisms to use. That is why we look at all three of the nutrients. We want to know how increases in all three nutrients might influence soil organisms. Which nutrient is most limiting might not be the same everywhere in the dry valleys, since the different areas have different geology. Hopefully this project will be able to tell us which nutrients are limiting in the different areas.

Katie and I are only at Bonney through tomorrow, then it's back to McMurdo to process our soil samples that we collect here. Hopefully, the final member of our team will arrive tomorrow. Ross's flight should be arriving tomorrow afternoon as we're returning from the field. Let's all hope that the good weather continues!