Tuesday, September 2, 2014

Soil biology of the Antarctic Peninsula

So far, the research I've done in Antarctica has been out of McMurdo Station. That's on the side of the continent closest to New Zealand and Australia. This coming field season, I will be doing my field work on the other side of the continent, along the Antarctic Peninsula. This is the piece of land that extends up towards South America.


Image from Wikipedia
The Antarctic Peninsula is one of the fastest changing regions on the planet. It is warming at one of the fastest rates on Earth. Also, invasive species are becoming an increasing problem. Invasive grasses and insects have been spotted along the Peninsula. Some of these species are accidentally brought from other continents by people. Also, because the Peninsula is warming, some Antarctic species can spread farther south into areas that used to be too cold for them to survive. This grass on the right, the Antarctic hair grass, has been spreading southward into new habitats.


Image from Nature Education
Of course, these changes in climate and invasive species can influence the biology living in the soil. If you're read my past posts, you'll know that the soil biology include bacteria, fungi, nematodes, mites, and other tiny invertebrates. The microscopic soil biology are the only year-round terrestrial animals on Antarctica. There are birds, seals, and penguins that live in Antarctica, but these are technically marine animals that sometimes come on land. Though the soil biology are small, they are the continent's only true inhabitants. This makes them very important to study, if we want to understand more about Antarctica!

From the hard work already done on the Antarctic Peninsula by many scientists, we know that the soil biology of the Peninsula is more abundant and diverse than in the McMurdo area where I usually work. That means there are more individuals from a larger number of species living in the soil in the Peninsula region. However, the Peninsula is a large area, and the soil biology in many places along the Peninsula have not been closely studied. We don't even know who lives where, and if we've seen all of the species that live there. How can we understand the impacts of this recent rapid change, if we don't even know who is there naturally?

Our research over the next couple of seasons will explore the diversity of soil biological communities along the entire Antarctic Peninsula. We will discover what species live in all of the places we visit. We will also compare who lives at each site with the plants and soil chemistry to understand how the environment influences the soil biology. That way, we can predict what will happen to the soil biology as the environment changes. Some of these species only live in Antarctica, so it's important to know how we can protect them. If they lose their home in Antarctica, they may be lost forever!


Wednesday, April 9, 2014

How to become a polar scientist

Are you interested in polar science? Are you curious about how polar ecosystems work and what kind of change is happening in them? Do you like going out to find the answers to your questions? Do you want to learn about and explore polar regions as a career?

When I was a kid, I didn't know I would become a field scientist in Antarctica. I wanted to be a veterinarian, because I liked animals. I didn't know that scientific research was a possible career. Once I realized that I could make a career out of studying animals outside in the natural world, I liked that idea much more! Then I realized that I could work all over the world, and my field work could happen in all sorts of places. I liked the adventure of travel, so I took an opportunity to work in Antarctica, and that's how I ended up doing what I do. I get to travel to many places around the world, ask questions about how the ecosystem works, then find out the answer to those questions. I have a pretty fun job!

Science in a penguin rookery
There are many fields of science that you can study in the Antarctic and Arctic. There are biologists and biogeochemists like me. Biologists can study invertebrates (like we do), microbes, plants, or the more charismatic animals like penguins, other birds, whales, and seals.
The Oden: icebreaker and  research vessel

There are also oceanographers who study ocean biogeochemistry and the movement of ocean water (circulation) around the polar region, which has an important role in understanding climate change.
Glaciologists study the composition and dynamics of the glaciers and ice sheets in the Antarctic and Arctic, where most of the planet's fresh water is stored. Many of them study climate change through the ice record.
Stream geochemists at work.
Geochemists study the elements found in the streams, glaciers, soil, and lakes.
Mt. Erebus
Other geologists study the rocks that make up the continent of Antarctica to understand how the continent formed, plus vulcanologists who study Mt. Erebus, the southern-most active volcano on the planet.

There are astronomers who work in Antarctica using telescopes or collecting meteorites, some even using it as a proxy for Mars. Atmospheric scientists study ozone and air quality, and physicists study subatomic particles.
Tools for LIDAR imagery
Geographers use satellite and radar imagery to map the continent. There are also engineers that run the satellites and telescopes. Historians document and preserve the 100+ years of human exploration of polar regions.

Click on any of the links in this paragraph to learn about that type of research. There are tons of things you can study in polar regions!


What do you have to do to become a polar scientist? Most polar scientists have college and graduate degrees (a masters degree and/or Ph.D.) in their particular field of science. (Or, they're students currently working towards achieving those degrees.) I went to college and earned a bachelors degree in biology, then went to graduate school to get a Ph.D. in ecology/biogeochemistry. If you want to become a polar scientist, it will involve working very hard in (and enjoying!) a lot of science classes. There are probably two basic characteristics that are true of every professional scientist: they're incredibly curious and willing to work very hard. Polar scientists also have an itch for adventure. The reward is that we get to make a career out of exploration to find answers to all of our questions!

Friday, March 14, 2014

Moribund Moss Rehydrating

In my previous post, you see two different photos of moss in the McMurdo Dry Valleys. In one photo, the moss is green. In the other, it's very grey and brown.

Because the Dry Valleys are so dry, normally moss is kind of shriveled and brown. It looks like it might be dead, but it's not! That stage is called "moribund", which basically means "looks dead." As soon as the moss gets wet, it perks right up! In the photo with the green moss, the moss had recently gotten wet from the flow of the stream.

Here's a video through the microscope of some moss. At first, it is shriveled and brown. As soon as I squirt some water onto it, though, the moss opens up and turns green again. I did not change the speed of the video. That's happening in real-time! (Sorry, the video was recorded using my phone through the eye-piece of the microscope, so it's not the greatest quality.)

video

In fact, a recent article shows how a little warmth, light, and water can revive moss that has been "long dead". Read about the 1500-year-old moss from Signy Island on the Antarctic Peninsula here.

Thursday, March 13, 2014

A tale of moss and soil in the Dry Valleys

I've posted before about some of our field work sampling moss in the McMurdo Dry Valleys.

 Moss are important to understand because, in the Dry Valleys, there are no other plants growing above the soil. Moss patches are the closest thing that the Dry Valleys have to forests! Sometimes the moss grows in small patches, like in the top photo on the left, but sometimes it's extensive, like the photo below it.

We want to understand the role moss play in the overall ecology of the Dry Valleys. How abundant are they across the ecosystem? How much nutrients do they take up from the environment? Where do their nutrients come from?

We traveled all around the Dry Valleys to collect moss from as many places as we could find. You can see an interactive map of all of the samples we collected by clicking here.Thanks to amazing satellite imagery, you can zoom in close enough to see the terrain at each of the spots where we took a moss sample!

We wanted to know whether moss can live everywhere in the Dry Valleys, or if there has to be very particular environmental conditions for them to grow. We compared soil chemistry in places where moss was growing with places where moss was not growing.  We learned that soils beneath moss tend to be slightly less salty and lower in pH (more neutral than basic) than soils without moss growing on them. That may be the result of the moss needing to grow in less salty, more neutral soil. (In other words, maybe the soil is already less salty and lower pH, so the moss are able to grow there.) Or, it could be that moss can grow anywhere and then turn the soil into something less salty and more neutral. (In other words, maybe the soil becomes less salty and lower in pH after the moss starts growing there.) We don't know yet! That's something we can look into with more experiments.

We also learned that there is a lot of variability in the nutrient content of moss. Sometimes the moss at one site differs in nutrient content from moss at another site. For example, moss growing at Canada Stream contained more nitrogen and phosphorus than moss growing at other places. (Those are the yellow dots in the graph below. They're higher up on the vertical axis than many of the other sites, which are the other color dots.) Moss growing in the Lake Bonney Basin had the lowest nitrogen and phosphorus content of the moss we sampled. (They're hard to pick out of the graph, though, because they're overlapped by so many other dots.) Often, though, the nutrient content in moss varies a lot within one site, making it hard to tell sites apart. Of the dozens of sites we visited, the only ones that seemed distinct in nutrient content were the extremely high and extremely low. The rest blend in with each other, as you can see in the graph.


We also learned that most of the nutrients in the moss come from the soil, rather than water. However, the soil doesn't explain everything. In the graph above, you see that as soil nitrogen and phosphorus increases (moving towards the right on the horizontal axis), moss nutrients also tend to increase (moving higher on the vertical axis), but there's a LOT of variability around that. The dots don't stay close to the line, but instead are scattered around.

(For those that are curious, the purple dot waaaay out to the right on the phosphorus graph is moss from one of the penguin rookeries. Penguin guano contains a lot of phosphorus!)

The relationships with soil are tighter than with water's levels of nutrients, though. That's why, in this graph below, the triangle representing moss nitrogen (N) content is closest to the arrow for soil N, not Stream or Groundwater N. The triangle for moss phosphorus (P) content is closest to soil PO4 (phosphate), not Stream or Ground PO4. You'll notice that the relationship between moss and soil N is a bit tighter than moss and soil P, though.


So what does all of this mean? If the pulse events that I describe in earlier posts make water more available in the future, moss may be able to grow more. We were hoping that we could predict how nutrient cycles would change by knowing the source of moss nutrients and how much they take up. However, we learned that their nutrient uptake is highly variable, which will make it hard to predict how nutrient cycling will change with that increase in moss growth. 

The results of this experiment are published in the article: Ball B. and Virginia R. 2014.  The ecological role of moss in a polar desert: Implications for aboveground-belowground and terrestrial-aquatic linkages. Polar Biology.

Saturday, February 15, 2014

Fertilizing soil microbes

A lot of our field work tries to answer the question of how extra nutrients (like carbon, nitrogen, and phosphorus) affect soil biology. You can read about one of those experiments here in a previous posts. Sometimes it can be hard to measure biological activity in the field, because weather conditions might be bad the day we're there to make the measurements. If it happens to be cloudy and cold, the bacteria and fungi in the soil won't be very active, and it will be hard to measure their respiration. To deal with that problem, we also run a lot of experiments in the laboratory where we can keep the soils under better weather conditions where they'll be more active. (We call it measuring their "potential" activity.)

We wanted to know how a bit more about how the microbes responded to the nitrogen fertilization. Do bacteria and fungi respond differently? Does nitrogen influence the amount of microbes in the soil, or just how active they are? How does the nutrient content already in the soil influence how the microbes respond to new nutrient additions?

In the lab, we set up "miniature Dry Valleys" in jars. Each one of the jars in the picture has soil from the Dry Valleys. Half have soil from Lake Fryxell basin (which is naturally higher in phosphorus) and the other half has soil from Lake Bonney basin (which is naturally higher in nitrogen). We added different amounts of nitrogen to the jars. Some received low levels, some received medium levels, and some received high levels. (Others received no nitrogen at all, which was our control.) We tested our hypothesis that increasing the level of nitrogen would increasingly stimulate biology at Fryxell, where nitrogen is less plentiful than phosphorus. However we hypothesized that, when nitrogen was already plentiful (at Bonney), the higher levels of nitrogen addition would actually be toxic to the soil microbes. That's because nitrogen exists in the soil as a salt, and too much nitrogen can make the soil too salty to be healthy for the microbes.

The jars are sealed tightly so that no gas can escape. That way, all of the CO2 produced by the microbes as they respire stays trapped inside the jar. In the center of the lid is a silicone disc. The silicone keeps the gas trapped inside, but as you can see in the photo to the left, I can insert a needle through the disc to remove a sample of gas. I then measure the CO2 that is contained in the gas sample I removed by injecting that sample into the machine you see below. We also counted the number of bacterial and fungal cells in the soil using a microscope.

What did we learn from this experiment? We found that microbes were only moderately influenced by nitrogen addition. As we predicted, the highest level of nitrogen had a negative effect on bacteria at Bonney (where nitrogen is already plentiful), because high levels of nitrogen become toxic to the bacteria. Fungi, however, weren't harmed by the high levels of nitrogen. Lower levels of nitrogen stimulated bacteria at Fryxell (where nitrogen is less plentiful), because adding more of a limiting nutrient allowed them to grow more and be more active.

What does all of this mean, in the big picture? It means that nitrogen fertilization can influence carbon dynamics in soils of the Dry Valleys. If future changes in the Dry Valleys bring more nitrogen to the soil, it's not only nitrogen that will change. Respiration means microbes are eating carbon in the soil, so the changing respiration we measured means the amount of carbon lost from the soil will also change. However, the way it changes will depend on where in the Dry Valleys you are. In some places, like Bonney, there may be less respiration and carbon loss, but in other places, like Fryxell, there may be more respiration and carbon loss.

The results of this experiment are published in this article: Ball B, Virginia R. 2014. Microbial biomass and respiration responses to nitrogen fertilization in a polar desert. Polar Biology 37(4): 573-585.

Thursday, March 14, 2013

Meltwater Seep Patches: The Results

During my field seasons, I blog about the field work we are conducting and the samples we collect. What do we do with all of the information we gather? When we finish measuring everything we want on the soil, we analyze the data, make graphs that show our results, and draw conclusions based on what we find. Here is an example:

A few seasons ago, you read about one of our field projects in which we were sampling meltwater seep patches. You can read about the field project from my blog post back in December of 2009. Seep patches appear as random wet spots in the soil. They're strange shapes and come in all sorts of sizes.
Here's a photo of me standing next to one of the larger seep patches.
The water making those wet patches is from ice. When snow, glaciers, or permafrost melt, that water percolates down through the soil. The water then moves through the bottom of the soil active layer with gravity. Because the air is so dry, the water can get drawn to the surface (when soil conditions are just right!) through capillary action. That's what makes a seep patch!

Recently, some summers have had major heat-waves, which causes extra melt and the appearance of more seep patches than usual. We wanted to know how those seep patches were changing the soil and the microscopic organisms living there. Obviously they're wetter, and that extra water can be very important for soil biology in a desert. But, what else gets put into the patches with that water? Nutrients can be dissolved in that water, which would also help fertilize soil biology. But, a lot of salts can also be dissolved in that water, which makes those seep patches not only wet, but also very salty. Salty environments can be harmful to soil biology.

To find out what conditions were like for soil biology inside the seep patches, we samples soil from inside seep patches to find out how much water, nutrients, and salts  were in the patches. That would tell us how good of a habitat they are for soil biology. We dug soil pits inside the seep patches to collect soil. We also dug soil pits outside the seep patches to see how inside compared to outside.
This is one of the seep patches we sampled. You can see little bags of soil at each soil pit we dug. After we took the soil samples, we filled the pits back in with the soil to minimize the damage we cause.
We sampled six seep patches that year. Here's a photo I took from a helicopter showing the area we sampled. Everywhere red number represents a seep patch that we sampled.

The inset at the bottom right shows our sampling method. The dark gray area represents a seep patch. At each of the six seep patches, we dug two bits at the Center of the seep patch (abbreviated Ca and Cb), two at the Edge of the seep patch (Ea and Eb), and two Outside the seep patch (Oa and Ob).

We took the soil from those pits back to the lab, and measured nutrient content and salt content. We learned that soil from inside the patch is a lot saltier than soil outside the patch.The graph below is made by an analysis called "principle components analysis" (abbreviated PCA). It's a bit difficult to explain, but in simple terms, it shows how each soil sample is related to the others in terms of salt content. Each symbol represents an individual soil sample. The soils from Center locations are circles. Soils from the Edge are squares, and soils from the Outside locations are diamonds. (Each sample is also labeled by the patch number and whether it was the "a" or "b", shown in the map above.) 
This is the graph made by an analysis called "Principle components analysis". It shows how each soil sample is related to the others in term of salt content

You can see in the graph that the Center and Edge samples cluster more towards the left side of the graph. There are also more arrows pointing towards the left side of the graph. Those arrows represent the salts that were measured in the soils. So, samples on the left side of the graph have higher amounts of those salts. The samples from Outside (the diamonds) cluster more towards the right, which means they're lower in those salts (because they're away from the arrows). The Outside samples also spread out a bit more. That means dry soils outside the seep patches are less salty, but pretty variable in salt content. Seep patches tend to make soils more similar to each other in that they are all very salty.

How does the soil biology respond to that saltier, wetter environment? What's more important for biology: getting the much-needed water or having to deal with the harmful salts? We took soil from the "Center" locations and the "Outside" locations and measured the amount of CO2 being respired. (Remember, respiration produces CO2, and we can measure respiration to tell us about how active the soil biology are.) We learned that not all patches are the same! Sometimes, there's more activity inside the seep patch, sometimes there's more activity outside the seep patch, and sometimes there's no difference!
This bar graph shows the amount of respiration (measured as "carbon mineralization") from inside and outside each of the six seep patches. Dark bars are the center of the patch, and the white bars are from outside the patch. The taller the bar, the more CO2 was respired from the soil, meaning the soil biology are more active.

We noticed that when the patch increased respiration (like Patch #1), the patch was much wetter but only somewhat saltier. That means the positive influence of water could overpower the negative influence of salts. When the patch decreased respiration (like Patch #2, 3, and 5), the patch was somewhat wetter but much saltier. That means the negative influence of salts can overpower the positive influence of water. So, the influence that seep patches have on soil biology depends on the relative size of the increase in water and the increase in salts.

Therefore, we are able to conclude that these meltwater seep patches aren't all the same. They will make the soils wetter and saltier at those spots, but they vary a bit in how much wetter or how much saltier the soil becomes. Since the relative increases in water and salt can cause the biology to respond in different ways, that means we can't predict how exactly a new seep patch will influence the soil biology. Future heat-waves and future climate warming will create more seep patches, which will create a lot of variability in the soil habitat and soil biological activity.

The citation for the paper publishing these results is: 
Ball, B. A. and R. A. Virginia. 2012. Meltwater seep patches increase heterogeneity of soil geochemistry and therefore habitat suitability. Geoderma 189-190:652-660.
You can also read more details about it in a poster presenting the results by clicking this link.

Tuesday, February 5, 2013

The OTHER Antarctic LTER

Much of my research in Antarctica has been through the National Science Foundation's Long-Term Ecological Research project (abbreviated LTER). I've worked in the dry valleys through the McMurdo LTER (abbreviated MCM). There is another Antarctic LTER that works on the other side of the continent: Palmer LTER (abbreviated PAL).


While our research in McMurdo is largely terrestrial (focusing on the land and planet Earth), Palmer LTER's research is mostly marine and oceanographic (focusing on the ocean). Want to learn more about what they do there? Here's a trailer for a documentary about some of the research happening at Palmer:
http://antarcticquest.rutgers.edu/