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Life’s Limits

It’s amazing to me that anything can live in the soils of the Dry Valleys. Even now, during the height of summer, conditions aren’t exactly cushy: soil temperatures on a warm day hover around 50 degrees F, the soils are very salty, and the availability of liquid water is patchy at best. Walking across the rough, rocky surface, it’s no wonder that early explorers and scientists declared the Dry Valleys devoid of life. And I haven’t even mentioned the winter – complete darkness, extreme cold, everything frozen solid.

This doesn't look like an easy place to live to me!

This doesn’t look like an easy place to live to me!

So how do they do it? How do we find living creatures in so many of the samples we collect? The animals living in these soils must be able to cope with indefinitely long periods without water in the frigid cold, but must also be able to react quickly to the presence of running water. They do so by going into anhydrobiosis, a state in which they are freeze-dried. All bodily functions stop (no eating, breathing, or reproducing) and remain on hold until conditions improve. While organisms in anhydrobiosis certainly appear dead, just add liquid water, and they’ll be squiggling around in no time!

Seals don't do nearly as well as nematodes in the Dry Valleys. Here's a leopard seal that somehow made it into Taylor Valley but didn't last long.

Seals don’t do nearly as well as nematodes in the Dry Valleys. Here’s a leopard seal that somehow made it into Taylor Valley but didn’t last long.

If these organisms have no trouble with extreme cold and extreme dry, what can stop them? For ecosystems everywhere – not just the harsh environment of the Dry Valleys – scientists like to know what limits life; we like to define the limiting nutrient. Imagine you’re baking a huge batch of chocolate chip cookies – as many cookies as possible. As you keep mixing batches of cookie dough, one ingredient is bound to run out first. Maybe it’s the chocolate chips. You have plenty of flour, sugar, and eggs, but what’s a chocolate chip cookie without the chocolate chips? The same thing happens in an ecosystem, only with nutrients instead of ingredients. There are many nutrients that are necessary for life, and if any of them are in short supply, then life is severely limited.

Life even exists under the Taylor Glacier! This is a picture of Blood Falls, where ancient brines seep out from under the glacier, oxidizing and turning red (like rust). Samples from Blood Falls contain living organisms!

Life even exists under the Taylor Glacier! This is a picture of Blood Falls, where ancient brines seep out from under the glacier, oxidizing and turning red (like rust). Samples from Blood Falls contain living organisms!

What’s the limiting nutrient in the Dry Valleys? Well, it depends. First of all, there aren’t a lot of any ingredients to start with. In Taylor Valley, the limiting nutrients changes as you head up the valley. Near the ocean, near Lake Fryxell, nitrogen is a limiting nutrient. Up at the top of the valley, near Lake Bonney, phosphorus limits life. In fact, Lake Bonney is one of the most phosphorus-limited ecosystems in the world! As I’ll explain in a future blog post, I’m interested in why the amount of phosphorus varies so much across the valley.

Lake Bonney is one of the most phosphorus-limited ecosystems in the world. And it's not a bad view, either!

Lake Bonney is one of the most phosphorus-limited ecosystems in the world. And it’s not a bad view, either!

Knowing the limiting nutrient in an ecosystem allows us to predict what will happen with any changes. How will life respond if more nutrients enter the system (something that may happen due to a warming climate)? We can test our predictions by artificially adding nutrients (like phosphorus and nitrogen), and then seeing what happens. To judge the response, we record things like nematode abundance and soil respiration, a measurement of the activity of organisms in the soil.

 

We use an instrument called a Li-Cor to measure soil respiration. We put an air-tight chamber down on the soil and measure how much carbon dioxide builds up over a short period of time.

We use an instrument called a Li-Cor to measure soil respiration. We put an air-tight chamber down on the soil and measure how much carbon dioxide builds up over a short period of time.

Now you get to make some predictions. What will happen near Lake Fryxell if we add nitrogen? What about phosphorus? And what will happen near Lake Bonney if we add nitrogen? What about phosphorus? Do you think these responses would continue forever with more and more of the added nutrient?

From my blog so far, it probably seems like I spend most of my time in the Dry Valleys among towering mountains and sparkling glaciers. Although taking in the stunning beauty of our field sites is important, this is a warped view of my time in Antarctica. The vast majority of my time is spent in the lab, doing simple, repetitive tasks. It’s quick and easy to collect hundreds of soil samples in the field, but it takes a lot longer to process and analyze those samples. For every single scoop of dirt collected in the Dry Valleys, we have to first label bags and containers, and then measure soil moisture, soil pH and conductivity, count nematodes, and prepare the samples to be sent back to the US for even more analyses!

Matt happily collects a soil sample in the field. That one sample will take hours of processing in the lab.

Matt happily collects a soil sample in the field. That one sample will take hours of processing in the lab.

So what do I really do all day?

I label plastic containers.

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I weigh soil. I weigh chemicals. I weigh more soil.

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I wash glassware.

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I fill plastic containers with water.

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Although these tasks can seem endless and boring, they never seem pointless. These simple, repetitive tasks are the backbone of the field ecology we do. The strength of our research comes from the fact that we collect many, many samples every single year. First, we have to keep track of all those samples (thus the labeling). Then we treat each sample in exactly the same way, using the same quantity of soil (thus the weighing), using clean containers (thus the washing) — even down to stirring the soil in water for the exact same amount of time!

Our experiments in the field are replicated, which means that we do the same thing over and over again to see if we always find the same result. When we want to know the impact of adding water to soils, we don’t just add water to one small area. We add it to many different small areas to see if they respond in the same way (thus the filling plastic containers with water).

Matt waters one of the many experimental plots.

Matt waters one of the many experimental plots.

Completing all of these repetitive tasks gives me time to think. And it’s got me thinking about how many skills we learn through repetition. How do you learn a musical instrument? Repetition. How do you learn a foreign language? Repetition. A team sport? The same. So many activities and skills require doing the same thing over and over again. Science is just the same.

Is there anything we learn that doesn’t require repetition? And, more personally, what do you enjoy about repetitive tasks? Do they ever drive you crazy?

While washing dishes can sometimes drive me crazy, I know that these small tasks are a crucial part of our whole operation. While labeling bags and bottles might seem trivial, our samples mean nothing unless they are identified. Our samples mean nothing unless we take each step of the process seriously, from scooping soil into bags to running the most technical analyses.

Now that you’ve had a chance to make your own predictions about how the Dry Valleys will respond to a warmer world, I want to take you through one of the predictions our lead scientists have made. I’ll also describe a big experiment that we just started to simulate the impacts of the warming climate on the Dry Valley ecosystem.

In the Dry Valleys, liquid water is precious. It determines where life can exist and it links glaciers, streams, soils, and lakes. As it flows across the landscape, it brings with it life and nutrients. With absolutely no liquid water coming out of the sky (all precipitation here falls as snow), melting ice and snow provide all the liquid water in the valleys. So what happens when it warms? Higher temperatures will lead to more melting, and more melting means more liquid water flowing across the landscape.

Streams connect glaciers, soils, and lakes, carrying organisms and nutrients. They also make hiking sometimes difficult.

Streams connect glaciers, soils, and lakes, carrying organisms and nutrients. They also make hiking sometimes difficult.

It’s easy to visualize glaciers and snow melting, but it’s harder to imagine the melting that will happen out of sight beneath our feet. Permafrost, or permanently frozen soil, hidden only tens of centimeters below the ground, will also respond to a warming climate. In the Arctic, thawing permafrost has already started causing problems – imagine roads and buildings, built on solid frozen ground, suddenly becoming unstable as the ground thaws beneath them. Will something similar happen in the Dry Valleys? What will permafrost thaw mean for life in the Dry Valleys? How will the additional liquid water change the ecosystem?

Glaciers aren't the only thing that can melt in the Dry Valleys. Permafrost, permanently frozen soil, can melt too!

Glaciers aren’t the only thing that can melt in the Dry Valleys. Permafrost, permanently frozen soil, can melt too!

That’s what the lead scientists were wondering when they designed the Pulse Press Project, meant to simulate permafrost melt along a hill slope. The basic idea behind the project is to add liquid water at the top of the hill, and to watch what happens as the water flows downhill. Because permafrost melt happens below the ground surface, the liquid water gets added to trenches so that the water flows through the soil rather than over the soil. The project is a long-term study, meaning that water will get added over the course of many years. Each year, the team will collect soil samples to see how the chemistry, soil moisture, and nematode abundance change as we add more liquid water.

The water is added to trenches so that it flows beneath the surface.

The water is added to trenches so that it flows beneath the surface.

All of this sounds good in theory, but how do you actually do this in the field? Well, you need a huge tank, a water pump, some tubes, and a huge amount of patience. The hill slope is conveniently located near a pond, so the first step is to pump that water uphill into a holding tank. The water then gets slowly released into trenches, and then we wait for the water to seep down the slope.

Water gets pumped into a large holding tank and then slowly released into the trenches.

Water gets pumped into a large holding tank and then slowly released into the trenches.

And wait. And wait some more. Apparently it takes a long time for water to flow downhill through the soil.

Waiting for the water to drain from the trenches. Big Science requires a lot of patience.

Waiting for the water to drain from the trenches. Big Science requires a lot of patience.

Although it felt like it was taking a long time, by the end of two days, all the water has been successfully applied! Now we wait until next year, when we’ll collect more soil samples and apply more water.

So, what do you think will happen to the hill slope? Will the abundance of nematodes change? Will the chemistry of the soil change? Will the hill change visibly, or will all the changes be hidden from the naked eye? Even the lead scientists don’t know the answers to these questions. And that’s what makes field research so exciting. We can make as many educated guesses as we like, but we can always be surprised by what actually happens.

The McMurdo Dry Valleys Long Term Ecological Research project has been running for more than 20 years and is a huge operation, with 12 principal investigators (lead scientists) and dozens of collaborators and graduate students from institutions across the Unites States and beyond. As I’m sure you can imagine, it can be hard to keep such a large group of people organized and focused. Just think about trying to do group projects with only 3 or 4 classmates!

Even just three lead scientists in the field can lead to a long decision-making process.

Even just three lead scientists in the field can lead to a long decision-making process.

One thing that keeps the project focused is the fact that every six years, the team submits a proposal to the National Science Foundation. In order to get money to fund the project, the lead scientists must show that they have a plan for the next six years. And one of the most important aspects of this plan is an overarching guiding question that the scientists hope to answer. This question is what keeps all the lead scientists on track – it’s their group project assignment. Right now, the big question has to do with climate warming: How will climate warming alter the McMurdo Dry Valley ecosystem? Based on more than 20 years of experience, the lead scientists have some ideas about what will happen. But rather than just give away their predictions, I want you to make your own. In order to do that, you need a little more information about the Dry Valleys.

What would this picture look like in a warmer world?

What would this picture look like in a warmer world?

As I mentioned in an earlier blog, the McMurdo Dry Valleys make up the largest area of ice-free land on the Antarctic continent. But the Dry Valley system isn’t just bare rock. There are numerous mountain glaciers flowing down into the valleys, ending abruptly in tall cliffs of ice. These glaciers are critical components of the Dry Valley system because they provide the majority of the liquid water that flows during the brief Antarctic summer. Streams, which flow for only two months out of the year, carry this glacier melt-water across the bare soils into lakes. As the water runs over rocks and soils, it picks up minerals and nutrients, carrying them into the lakes as well.

Glaciers flow down into the Dry Valleys, ending in cliffs of ice. How will the glaciers change in a warming world?

Glaciers flow down into the Dry Valleys, ending in cliffs of ice. How will the glaciers change in a warming world?

Streams, which flow for only two months out of the year, carry this glacier melt-water across the bare soils into lakes. As the water runs over rocks and soils, it picks up minerals and nutrients, carrying them into the lakes as well. During the summer, only the very top layer of soil thaws – dig down less than a foot, and you’ll hit frozen soil, or permafrost. Lakes in the Dry Valleys are unlike any lakes we have in the Northeast – they are always covered in a thick layer of ice, even in the height of summer. Water underneath the ice remains liquid throughout the entire year, but it is separated from the rest of the world by a solid sheet of ice.

Lake Fryxell, covered in ice even in the height of summer. What will happen to the lakes in a warmer world?

Lake Fryxell, covered in ice even in the height of summer. What will happen to the lakes in a warmer world?

Glaciers, streams, soils, and lakes are the physical parts of the Dry Valleys – but there is life found everywhere. Moss and algae can be seen by the naked eye, but hundreds of other organisms, too small for us to see, live in the soils, streams, lakes, and glaciers of the Dry Valleys.

So, with this introduction to the Dry Valleys, think about how the system might change with a warming climate. It might be helpful to consider each component (glaciers, streams, soils, and lakes) separately, but remember that they are all linked. In my next blog, I’ll discuss one of the predictions that the lead scientists have. First though, you have to make your own predictions!

One thing that surprised me when I arrived in Antarctica was the scale of McMurdo, the largest US base on the continent. With a current population of 761, McMurdo has to provide a lot of services: running drinkable water, electricity, health care, emergency response, food services, and entertainment – just to name a few. There’s a chapel, a fire station (and fire trucks), a store – everything to make it seem like a real town.

An aerial view of McMurdo. It's quite a town!

An aerial view of McMurdo. It’s quite a town!

In McMurdo, just like at home, it’s easy to turn on the light and forget about the cost of electricity. It’s easy to turn on the faucet and forget where the water comes from, or throw a napkin away and not think about where it will end up. While this is problematic anywhere, it is especially concerning in McMurdo, where every drop of water or flash of light requires a long chain of steps, each one requiring both energy and time.

Power lines criss-cross the town. Although there are three wind turbines on the ridge above town, McMurdo relies on hydrocarbons for power.

Power lines criss-cross the town. Although there are three wind turbines on the ridge above town, McMurdo relies on hydrocarbons for power.

Every drop of fresh water we drink in McMurdo begins as seawater. It first goes through an energy-intensive Reverse Osmosis system that removes the salt, making fresh water. However, since Reverse Osmosis removes everything in the water, even the beneficial minerals, the water department in McMurdo then has to add these components back to the water before we can pour a cup.

The sink in my room makes it easy to forget where the water comes from. Just turn the tap, and there's plenty of fresh water!

The sink in my room makes it easy to forget where the water comes from. Just turn the tap, and there’s plenty of fresh water!

Trash is another good example of our energy impact here in McMurdo. The napkin I just threw away will be one of the best-travelled napkins by the time it ends up in a landfill. Clearly, it started its life somewhere off continent (last I checked, there weren’t any napkin factories in Antarctica). No trash is allowed to remain on the Antarctic continent (there are very strict conservation laws governing our behavior here), so the napkin, along with all other waste produced here (even human waste!) will eventually travel back to the United States and end up in a landfill there. That’s a journey most people will never even get to experience!

Boxes and boxes of well-sorted trash and recycling are all over McMurdo. None of it will remain on the continent -- it will all be shipped back to the United States.

Boxes and boxes of well-sorted trash and recycling are all over McMurdo. None of it will remain on the continent — it will all be shipped back to the United States.

Since the cost of water, electricity, and waste is so great, there are many ways we try to conserve. Trash and recycling sorting is incredibly important and complicated here so that as much energy as possible can be saved in the process. McMurdo residents are asked to take short, infrequent showers. Field camps run on renewable energy as much as possible. And yet, there are certain things that can’t be given up: all 761 residents need to be well hydrated (and it’s a very dry continent, so dehydration is a real health risk), we all need to wash our hands, and the science we do here also requires a lot of energy and water use. So although we can try to reduce our impact, the cost of running a town in Antarctica is very high.

Think your electricity bill is expensive? Here's the cost at McMurdo.

Think your electricity bill is expensive? Here’s the cost at McMurdo.

Wouldn’t it be great if we could conduct important science in Antarctica while minimizing our energy footprint? Here’s my challenge to you: What can we do to reduce our impact here in McMurdo? How can we conserve energy? If you were in Antarctica, what would you be willing to do to reduce the cost?

And finally, since this is my first blog of 2014, I have to show one picture of Icestock, McMurdo’s musical New Year’s Eve celebration. Holidays are definitely not something that we conserve energy for in Antarctica!

The 25th Annual Icestock: Too Big to Fail!

The 25th Annual Icestock: Too Big to Fail!

In MacTown Once More

I’ve made it! After many long days of traveling and preparation, I’m finally in MacTown once more. Although a lot has happened since last year, it almost feels as though I’ve never left. Familiar faces in the Galley, familiar sights, familiar routines.

But I’m getting ahead of myself. Last time, I promised to describe how we get from Christchurch to Antarctica. Upon arriving in Christchurch, our first order of business is getting our Extreme Cold Weather gear (ECW): lots of fleece layers, hats, mittens, huge white boots, and – most importantly – a huge red parka (Big Red).

The Clothing Distribution Center in Christchurch has rows and rows of Extreme Cold Weather gear.

The Clothing Distribution Center in Christchurch has rows and rows of Extreme Cold Weather gear.

Cubbies full of Bunny Boots, the big white boots we're required to wear on all flights.

Cubbies full of Bunny Boots, the big white boots we’re required to wear on all flights.

Equipped with all these warm layers, we’re ready to make the 8-hour flight from Christchurch to McMurdo (also known as MacTown), the main US base in Antarctica.

This flight, on an LC-130 (for those of you who know something about military planes), is unlike any commercial flight. First of all, we’re required to wear our Big Red, boots, and wind pants. Pictures are the best way to describe the interior of the plane.

Lined up in the LC-130.

Lined up in the LC-130.

Big Red makes it easier to nap during the endless flight.

Big Red makes it easier to nap during the endless flight.

Other things that make the trip unique include the noise (earplugs are an absolute necessity) and the incredible views.

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After landing on the ice (the LC-130 has skis!), we then have an hour drive to McMurdo, which is located on solid rock on Ross Island (check out a map of Antarctica to see where that is).

Now that we’re here, our first order of business is to set up our lab space. Although we get the same lab each year, at the end of every season we have to pack everything away. So now, we’re faced with the daunting task of unpacking, organizing, cleaning, and getting ready for our first samples.

Matt is a little daunted by the number of boxes we have to unpack and organize.

Matt is a little daunted by the number of boxes we have to unpack and organize.

The other main task is to complete all of the safety trainings that the United States Antarctic Program requires before we head out to do our science. This includes information about cold injuries, basic camping, risk assessment, and helicopter safety. All this training has me thinking about the risks involved in doing Antarctic field science: the cold, the rapidly changing weather, the distance from help. And yet, the accidents that happen here are the same accidents that happen anywhere: trips, falls, and scrapes.

So here’s my question to you: if you were to come to Antarctica to do field science, what would you be the most nervous about? What would you want training in? And so I don’t end on that note, what would you be the most excited about?

The conventional view of lakes is that they are active (organisms grow, nutrients cycle) during ice-free periods, and are inactive when covered by ice. This is a convenient worldview to have, as most scientists are busy teaching courses and shy away from the logistically difficult field conditions winter presents (myself included). However, the notion that lakes are essentially “on hold” during winter months may be due more to a lack of data on under-ice processes rather than a lack of interesting biology and biogeochemistry occurring under the ice.

I’ve been working an interdisciplinary group of microbiologists, physical limnologists (scientists who study the physics of lakes), and ecologists to synthesize what is known about microorganisms under ice. We recently finished writing a paper that synthesizes existing research to show that winter may actually be important for microorganisms and what occurs in lakes during the rest of the year.

Winter field work. Photo E. Traver

Winter field work. Photo E. Traver

As the duration of ice cover has begun to decrease in many parts of the world, it is important to continue research aimed at better understanding under ice dynamics. For more information, here is an open access link to our paper: http://aslo.org/lo/toc/vol_58/issue_6/1998.pdf

 

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